CORE JAVA

class Fibonacci{  
public static void main(String args[])  
{    
 int n1=0,n2=1,n3,i,count=10;    
 System.out.print(n1+" "+n2);//printing 0 and 1    
    
 for(i=2;i<count;++i)//loop starts from 2 because 0 and 1 are already printed    
 {    
  n3=n1+n2;    
  System.out.print(" "+n3);    
  n1=n2;    
  n2=n3;    
 }      
}
} 

Output: 0 1 1 2 3 5 8 13 21 34
public class Prime{    
 public static void main(String args[]){    
  int i,m=0,flag=0;      
  int n=3;//it is the number to be checked    
  m=n/2;      
  if(n==0||n==1){  
   System.out.println(n+" is not prime number");      
  }else{  
   for(i=2;i<=m;i++){      
    if(n%i==0){      
     System.out.println(n+" is not prime number");      
     flag=1;      
     break;      
    }      
   }      
   if(flag==0)  { System.out.println(n+" is prime number"); }  
  }//end of else  
}    
}   

Output:
3 is prime number
public class Palindrome
{
    public static void main(String args[])
    {
        String a, b = "";
        Scanner s = new Scanner(System.in);
        System.out.print("Enter the string you want to check:");
        a = s.nextLine();
        int n = a.length();
        for(int i = n - 1; i >= 0; i--)
        {
            b = b + a.charAt(i);
        }
        if(a.equalsIgnoreCase(b))
        {
            System.out.println("The string is palindrome.");
        }
        else
        {
            System.out.println("The string is not palindrome.");
        }
    }
}
Output:

Enter the string you want to check: abba
The string is palindrome.
class Palindrome{  
 public static void main(String args[]){  
  int r,sum=0,temp;    
  int n=313;//It is the number variable to be checked for palindrome  
  
  temp=n;    
  while(n>0){    
   r=n%10;  //getting remainder  
   sum=(sum*10)+r;    
   n=n/10;    
  }    
  if(temp==sum)    
   System.out.println("Palindrome Number ");    
  else    
   System.out.println("not palindrome");    
}  
}  
Output:

Palindrome Number
class Armstrong{  
  public static void main(String[] args)  {  
    int c=0,a,temp;  
    int n=371;//It is the number to check armstrong  
    temp=n;  
    while(n>0)  
    {  
    a=n%10;  
    n=n/10;  
    c=c+(a*a*a);  
    }  
    if(temp==c)  
    System.out.println("Armstrong Number");   
    else  
        System.out.println("Not Armstrong Number");   
   }  
}  
Output:

Armstrong Number
class Factorial{  
 public static void main(String args[]){  
  int i,fact=1;  
  int number=6;//It is the number to calculate factorial    
  for(i=1;i<=number;i++){    
      fact=fact*i;    
  }    
  System.out.println("Factorial of "+number+" is: "+fact);    
 }  
}  
Output:

Factorial of 6 is: 720
1) By StringBuilder / StringBuffer

public class StringFormatter {  
public static String reverseString(String str){  
    StringBuilder sb=new StringBuilder(str);  
    sb.reverse();  
    return sb.toString();  
}  
}  

public class TestStringFormatter {  
public static void main(String[] args) {  
    System.out.println(StringFormatter.reverseString("India"));  
    System.out.println(StringFormatter.reverseString("Hindustan"));      
    }  
}  
Output:
aidnI
natsudniH
2) By Reverse Iteration

public class StringFormatter {  
public static String reverseString(String str){  
    char ch[]=str.toCharArray();  
    String rev="";  
    for(int i=ch.length-1;i>=0;i--){  
        rev+=ch[i];  
    }  
    return rev;  
}  
}  

public class TestStringFormatter {  
public static void main(String[] args) {  
    System.out.println(StringFormatter.reverseString("India"));  
    System.out.println(StringFormatter.reverseString("Hindustan"));      
    }  
}  
Output:
aidnI
natsudniH
public class RemoveDuplicate{
  
public static int removeDuplicate(int arr[], int n){  
        if (n==0 || n==1){  
            return n;  
        }  
        int[] temp = new int[n];  
        int j = 0;  
        for (int i=0; i<n-1; i++){  
            if (arr[i] != arr[i+1]){  
                temp[j++] = arr[i];  
            }  
         }  
        temp[j++] = arr[n-1];     
        // Changing original array  
        for (int i=0; i<j; i++){  
            arr[i] = temp[i];  
        }  
        return j;  
    }  
       
    public static void main (String[] args) {  
        int arr[] = {5,10,20,20,30,5,30,40,50,50};  
        int length = arr.length;  
        length = removeDuplicate(arr, length);  
        //printing array elements  
        for (int i=0; i<length; i++)  
           System.out.print(arr[i]+" ");  
    }  
}  

Output:

5 10 20 30 40 50 
public class Squareroot {
	private static Scanner c;
	public static void main(String[] args) 
	{
		double number, squareRoot;
		c = new Scanner(System.in);
		
		System.out.print(" Please Enter any Number : ");
		number = c.nextDouble();		
		
		squareRoot = Math.sqrt(number);
		
		System.out.println("\n The Square of a Given Number  " + number + "  =  " + squareRoot);
	}
}

Output:
Please enter any number : 144
The Square of a Given Number 144 is 12.0
import java.io.*; 
import java.util.*; 
  
class Reverse { 
  
// reverses individual words of a string 
static void reverseWords(String str) 
{ 
    Stack st=new Stack(); 
   
    // Traverse given string  
    for (int i = 0; i < str.length(); ++i) { 
        if (str.charAt(i) != ' ') 
            st.push(str.charAt(i)); 
    
        else { 
            while (st.empty() == false) { 
                System.out.print(st.pop()); 
                  
            } 
            System.out.print(" "); 
        } 
    } 
   
    while (st.empty() == false) { 
        System.out.print(st.pop()); 
          
    } 
} 
   
public static void main(String[] args) 
{ 
   String str = "Hello World"; 
    reverseWords(str); 
  } 
} 

Output:
dlroW olleH
public class Anagram {  
    static void isAnagram(String str1, String str2) {  
        String s1 = str1.replaceAll("\\s", "");  
        String s2 = str2.replaceAll("\\s", "");  
        boolean status = true;  
        if (s1.length() != s2.length()) {  
            status = false;  
        } else {  
            char[] ArrayS1 = s1.toLowerCase().toCharArray();  
            char[] ArrayS2 = s2.toLowerCase().toCharArray();  
            Arrays.sort(ArrayS1);  
            Arrays.sort(ArrayS2);  
            status = Arrays.equals(ArrayS1, ArrayS2);  
        }  
        if (status) {  
            System.out.println(s1 + " and " + s2 + " are anagrams");  
        } else {  
            System.out.println(s1 + " and " + s2 + " are not anagrams");  
        }  
    }  
   
    public static void main(String[] args) {  
        isAnagram("Road", "Roar");  
        isAnagram("Website", "Android");  
    }  
}  
Output:

Road and Roar are anagrams
Website and Android are anagrams
public class LeapYear {

public static void main(String[] args) {
 
//year we want to check int year = 2004;
//if year is divisible by 4, it is a leap year

if(year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0)) System.out.println("Year " + year + " is a leap year");
else

System.out.println("Year " + year + " is not a leap year");

}

}

Output :
Year 2004 is a leap year
public class PrintNumbers
{
    public static void main(String[] args)
    {
        for(int i=1; i<=1000; i++)
        {
            System.out.println(i);
        }
    }
}
public class SumNumbers
{
    public static void main(String[] args)
    {
        int sum = 0;
        for(int i=1; i<=20; i++)
        {
            sum += i;
        }
        System.out.println("Sum: " + sum);
    }
}
import java.util.Scanner;
 
public class DecimalToBinary
{   
    public static void main(String[] args) 
    {
        Scanner scanner = new Scanner(System.in);
         
        System.out.println("Enter Decimal Number : ");
         
        int inputNumber = scanner.nextInt();
         
        int copyOfInputNumber = inputNumber;
         
        String binary = "";
         
        int rem = 0;
         
        while (inputNumber > 0)
        {
            rem = inputNumber % 2;
             
            binary =  rem + binary;
             
            inputNumber = inputNumber/2;
        }
         
        System.out.println("Binary of "+copyOfInputNumber+" is "+binary);
    }
}
Output :

Enter Decimal Number :
30
Binary of 30 is 11110
import java.util.Scanner;
 
public class DecimalToOctal
{   
    public static void main(String[] args) 
    {
        Scanner scanner = new Scanner(System.in);
         
        System.out.println("Enter Decimal Number : ");
         
        int inputNumber = scanner.nextInt();
         
        int copyOfInputNumber = inputNumber;
         
        String octal = "";
         
        int rem = 0;
         
        while (inputNumber > 0)
        {
            rem = inputNumber%8;
             
            octal =  rem + octal;
             
            inputNumber = inputNumber/8;
        }
         
        System.out.println("Octal of "+copyOfInputNumber+" is "+octal);
    }
}
Output :

Enter Decimal Number :
250
Octal of 250 is 372
import java.util.Scanner;
 
public class DecimalToHexaDecimal
{   
    public static void main(String[] args) 
    {
        Scanner scanner= new Scanner(System.in);
     
        System.out.println("Enter Decimal Number : ");
         
        int inputNumber = scanner.nextInt();
         
        int copyOfInputNumber = inputNumber;
         
        String hexa = "";
         
        char hexaDecimals[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
         
        int rem = 0;
         
        while (inputNumber > 0)
        {
            rem = inputNumber%16;
             
            hexa =  hexaDecimals[rem] + hexa;
             
            inputNumber = inputNumber/16;
        }
         
        System.out.println("HexaDecimal of "+copyOfInputNumber+" is "+hexa);
    }
}
Output :

Enter Decimal Number :
1500
HexaDecimal of 1500 is 5DC
import java.util.Scanner;

public class ReadIntegers
{
    public static void main(String[] args)
    {
        Scanner console = new Scanner(System.in);
     
        int number;
        char choice;
        int evenSum = 0;
        int oddSum = 0;
        
        do
        {
            System.out.print("Enter the number ");
            number = console.nextInt();
        
            if( number % 2 == 0)
            {
                evenSum += number;
            }
            else
            {
                oddSum += number;
            }
        
            System.out.print("Do you want to continue y/n? ");
            choice = console.next().charAt(0);
            
        }while(choice=='y' || choice == 'Y');
        
        System.out.println("Sum of even numbers: " + evenSum);
        System.out.println("Sum of odd numbers: " + oddSum);
    }  
}
public class MainClass
{
    public static void main(String[] args)
    {
        ArrayList list = new ArrayList();
 
        list.add("PHP");
 
        list.add("Python");
 
        list.add("C");
 
        list.add("SERVLETS");
 
        list.add("J2EE");
 
        System.out.println(list);      
 
        Object[] array = list.toArray();
 
        for (Object object : array)
        {
            System.out.println(object);
        }
 
    }
}

Output:
PHP
Python
C
Servlet
J2EE
public class MainClass
{
    public static void main(String[] args)
    {
        ArrayList al = new ArrayList();
 
        al.add("First");
 
        al.add("Second");
 
        al.add("Third");
 
        al.add("Fourth");
 
        System.out.println(list);    
 
        //Inserting "A" at index 1
 
        al.add(1, "A");
 
        //Inserting "B" at index 3
 
        al.add(3, "B");
 
        System.out.println(al);   
    }
}

Output:
[First, A, Second, B, Third, Fourth]
public class MainClass
{
    public static void main(String[] args)
    {
        ArrayList al = new ArrayList();
 
        al.add("A");
 
        al.add("B");
 
        al.add("C");
        
        al.add("D");
 
        System.out.println(al);    
 
        //Removing an element from position 2
 
        al.remove(2);
 
        System.out.println(al);    
        //Removing an element from position 3
 
        al.remove(3);
 
        System.out.println(al);   
    }
}

Output:
[A,B,C,D]
[A,B,D]
[A,B]
public class MainClass
{
    public static void main(String[] args)
    {
        ArrayList al = new ArrayList();
 
        al.add(1);
 
        al.add(2);
 
        al.add(3);
 
        al.add(4);
 
        al.add(5);
 
        al.add(6);
 
        System.out.println(al);    
 
        //Retrieving a SubList
 
        List subList = al.subList(1, 4);
 
        System.out.println(subList);    //Output : [2, 3, 4]
 
        //Modifying the list
 
        al.set(2, 0);
 
        //Changes will be reflected in subList
 
        System.out.println(subList);    //Output : [2, 0, 4]
 
        //Modifying the subList
 
        subList.set(2, 0);
 
        //Changes will be reflected in list
 
        System.out.println(al);    //Output : [1, 2, 0, 0, 5, 6]
    }
}

Output:
[1 2 3 4 5 6]
[2 3 4]
[2 0 4]
[1 2 0 0 5 6]
public class MainClass
{
    public static void main(String[] args)
    {   
        ArrayList al = new ArrayList();
         
        al.add(1);
         
        al.add(2);
         
        al.add(3);
         
        al.add(4);
         
        System.out.println(al);     //Output : [1, 2, 3, 4]
         
        ArrayList list = new ArrayList();
         
        list.add(5);
         
        list.add(6);
         
        list.add(7);
         
        list.add(8);
 
        System.out.println(list);    //Output : [5, 6, 7, 8]
         
        //Inserting all elements of list at index 2 of al
         
        list1.addAll(2, list);
         
        System.out.println(al);    //Output : [1, 2, 5, 6, 7, 8, 3, 4]
    }
}
import java.util.Arrays;

public class MainClass {
   public static void main(String args[]) throws Exception {
      int array[] = { 4, 2, -7 , 9, -25, 19, 14, -35 };
      Arrays.sort(array);
      printArray("Sorted array", array);
      int index = Arrays.binarySearch(array, 4);
      System.out.println("Found 4 @ " + index);
   }
   private static void printArray(String message, int array[]) {
      System.out.println(message + ": [length: " + array.length + "]");
      
      for (int i = 0; i < array.length; i++) {
         if(i != 0) {
            System.out.print(", ");
         }
         System.out.print(array[i]);                     
      }
      System.out.println();
   }
} 
Output :-
Sorted array: [length: 8]
-35 -25 -7 2 4 9 14 19 
Found 4 @ 4
import java.util.Arrays;

public class MainClass {
   public static void main(String args[]) throws Exception {
      int array[] = { 4, 2, -7 , 9, -25, 19, 14, -35 };
      Arrays.sort(array);
      printArray("Sorted array", array);
      
      int index = Arrays.binarySearch(array, 1);
      System.out.println("Didn't find 1 @ " + index);
      
      int newIndex = -index - 1;
      array = insertElement(array, 1, newIndex);
      printArray("With 1 added", array);
   }
   private static void printArray(String message, int array[]) {
      System.out.println(message + ": [length: " + array.length + "]");
      for (int i = 0; i < array.length; i++) {
         if (i != 0){
            System.out.print(", ");
         }
         System.out.print(array[i]);         
      }
      System.out.println();
   }
   private static int[] insertElement(int original[], int element, int index) {
      int length = original.length;
      int destination[] = new int[length + 1];
      System.arraycopy(original, 0, destination, 0, index);
      destination[index] = element;
      System.arraycopy(original, index, destination, index + 1, length - index);
      return destination;
   }
}

Output:

Sorted array: [length: 8]
-35 -25 -7 2 4 9 14 19 
Didn't find 1 @ 5
With 1 added: [length: 9]
-35 -25 -7 2 4 1 9 14 19 
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
   public static void main(String args[]) {
      String a[] = { "K", "O", "D" };
      String b[] = { "N", "E", "S", "T" };
      List list = new ArrayList(Arrays.asList(a));
      list.addAll(Arrays.asList(b));
      Object[] c = list.toArray();
      System.out.println(Arrays.toString(c));
   }
}

Output:
[K, O, D, N, E, S, T]

$ $ $ $ $ $ $ $ $
$ $ $ $ $ $ $
$ $ $ $ $
$ $ $
$

public class Pattern {

    public static void main(String[] args) {
        int rows = 5;

        for(int i = rows; i >= 1; --i) {
            for(int space = 1; space <= rows - i; ++space) {
                System.out.print("  ");
            }

            for(int j=i; j <= 2 * i - 1; ++j) {
                System.out.print("$ ");
            }

            for(int j = 0; j < i - 1; ++j) {
                System.out.print("$ ");
            }

            System.out.println();
        }
    }
}
import java.util.Arrays;

public class Main {
   public static void main(String[] args) throws Exception {
      int[] arry = {2,3,5,7,9,10};
      int[] arry1 = {2,3,5,7,9,10};
      int[] arry2 = {1,2,3,4};
      System.out.println("Is array 1 equal to array 2? " +Arrays.equals(arry, arry1));
      System.out.println("Is array 1 equal to array 3? " +Arrays.equals(arry, arry2));
   }
}

Output:
Is array 1 equal to array 2? true
Is array 1 equal to array 3? false
import java.util.*;

public class arrayList {
	public static void main(String[] args) {
		ArrayList al = new ArrayList();
		al.add("5");
		al.add("10");
		al.add("15");
		System.out.println(al.size());
		System.out.println("While Loop:");
		Iterator itr = al.iterator();
		while(itr.hasNext()) {
			System.out.println(itr.next());
		}
		System.out.println("Advanced For Loop:");
		for(Object obj : al) {
			System.out.println(obj);
	}
		System.out.println("For Loop:");
		for(int i=0; i<list.size(); i++) {
			System.out.println(al.get(i));
		}
}
}

Output:

3
While Loop:
5
10
15
Advanced For Loop:
5
10
15
For Loop:
5
10
15
public class MainClass
{
    static int secondLargest(int[] input)
    {
        int firstLargest, secondLargest;
 
        //Checking elements of input array
 
        if(input[0] > input[1])
        {
            //If first element is greater than second element
 
            firstLargest = input[0];
 
            secondLargest = input[1];
        }
        else
        {
            //If second element is greater than first element
 
            firstLargest = input[1];
 
            secondLargest = input[0];
        }
 
        //Checking remaining elements of input array
 
        for (int i = 2; i < input.length; i++)
        {
            if(input[i] > firstLargest)
            {
 
                secondLargest = firstLargest;
 
                firstLargest = input[i];
            }
            else if (input[i] < firstLargest && input[i] > secondLargest)
            {
                secondLargest = input[i];
            }
        }
 
        return secondLargest;
    }
 
    public static void main(String[] args)
    {
        System.out.println(secondLargest(new int[] {25, 12, 10, 33, 4, 90}));
 
        System.out.println(secondLargest(new int[] {122, 150, 108, 298, 399}));
 
        System.out.println(secondLargest(new int[] {1202, 1543, 1011, 2584, 5894}));
 
    }
}
Output :
10
122
1202
public class MissingNumber
{
    static int sumOfNnumbers(int n)
    {
        int sum = (n * (n+1))/ 2;
 
        return sum;
    }
 
    static int sumOfElements(int[] array)
    {
        int sum = 0;
 
        for (int i = 0; i < array.length; i++)
        {
            sum = sum + array[i];
        }
 
        return sum;
    }
 
    public static void main(String[] args)
    {
        int n = 8;
 
        int[] a = {1, 5, 2, 3, 7, 6, 8};
 
        int sumOfNnumbers = sumOfNnumbers(n);
 
        int sumOfElements = sumOfElements(a);
 
        int missingNumber = sumOfNnumbers - sumOfElements;
 
        System.out.println("Missing Number is = "+missingNumber);
    }
}
import java.util.Scanner;
 
public class MainClass
{   
    public static void main(String[] args) 
    {
         
        String[] romanSymbols = {"I", "IV", "V", "IX", "X", "XL", "L", "XC", "X", "CD", "D", "CM", "M"};
         
         
        int[] decimals = {1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000};
         
        Scanner scanner = new Scanner(System.in);
         
        System.out.println("Enter The Decimal Number Between 1 and 2999");
         
        int inputNumber = scanner.nextInt();
         
        int copyOfInputNumber = inputNumber;
         
        String roman = "";
         
        if (inputNumber >= 1 && inputNumber <= 2999)
        {
            for (int i = 0; i < 13; i++) 
            {
                while(inputNumber >= decimals[i])
                {
                    inputNumber = inputNumber - decimals[i];
                     
                    roman = roman + romanSymbols[i];
                }
            }
             
            System.out.println("Roman Value Of "+copyOfInputNumber+" is : "+roman);
        }
        else
        {
            System.out.println("Not a valid number");
        }
    }
}
Output :

Enter The Decimal Number Between 1 and 2999
1269
Roman Value Of 1269 is : MCCLXIX
public class SeparateZeros
{
    static void moveZerosToEnd(int inputArray[])
    {
        int counter = 0;
 
        for (int i = 0; i < inputArray.length; i++)
        {
            if(inputArray[i] != 0)
            {
                inputArray[counter] = inputArray[i];
 
                //Incrementing the counter by 1
 
                counter++;
            }
        }
 
        //Assigning zero to remaining elements
 
        while (counter < inputArray.length)
        {
            inputArray[counter] = 0;
 
            counter++;
        }
 
        System.out.println(Arrays.toString(inputArray));
    }
 
    public static void main(String[] args)
    {
        moveZerosToEnd(new int[] {4, 10, 20, 0, 30, 0, 8});
 
        moveZerosToEnd(new int[] {-9, 0, 12, 24, 0, 15, 0, 22});

    }
}
Output :

[4, 10, 20, 30, 8, 0, 0]
[-9, 12, 24, 15, 22, 0, 0]
public class SeparateZeros
{
    static void moveZerosToFront(int inputArray[])
    {
        int counter = inputArray.length-1;
 
        for (int i = inputArray.length-1; i >= 0; i--)
        {
            if(inputArray[i] != 0)
            {
                inputArray[counter] = inputArray[i];
 
                counter--;
            }
        }
 
        while (counter >= 0)
        {
            inputArray[counter] = 0;
 
            counter--;
        }
 
        System.out.println(Arrays.toString(inputArray));
    }
 
    public static void main(String[] args)
    {
        moveZerosToFront(new int[] {4, 10, 20, 0, 30, 0, 8});
 
        moveZerosToFront(new int[] {-9, 0, 12, 24, 0, 15, 0, 22});
 
    }
}

Output:
[0, 0, 4, 10, 20, 30, 8]
[0, 0, -9, 12, 24, 15, 22]
class CharCountInString
{
    static void characterCount(String inputString)
    {
        
 
        HashMap<Character, Integer> charCountMap = new HashMap<Character, Integer>();
 
        //Converting given string to char array
 
        char[] strArray = inputString.toCharArray();
 
        
        for (char c : strArray)
        {
            if(charCountMap.containsKey(c))
            {
        
                charCountMap.put(c, charCountMap.get(c)+1);
            }
            else
            {
        
 
                charCountMap.put(c, 1);
            }
        }
 
        
        System.out.println(charCountMap);
    }
 
    public static void main(String[] args)
    {
       characterCount("Internationalization");
 
    }
}
Output :

{I=1, n=4, t=2, e=1, r=1, a=3, i=3, z=1, o=2}
public class StringPermutations {

    public static void main(String args[]) {
        permutation("123");
    }

 
   public static void permutation(String input){
          permutation("", input);
   }
  private static void permutation(String perm, String word) {
        if (word.isEmpty()) {
            System.err.println(perm + word);

        } else {
            for (int i = 0; i < word.length(); i++) {
                permutation(perm + word.charAt(i), word.substring(0, i) 
                                        + word.substring(i + 1, word.length()));
            }
        }

    }
}

Output:
123
132
213
231
312
321

1) Using replaceAll() Method.

In the first method, we use replaceAll() method of String class to remove all white spaces (including tab also) from a string. This is the one of the easiest method to remove all white spaces from a string. This method takes two parameters. One is the string to be replaced and another one is the string to be replaced with. We pass the string “\s” to be replaced with an empty string “”.

2) Without Using replaceAll() Method.

In the second method, we remove all white spaces (including tab also) from a string without using replaceAll() method. First we convert the given string to char array and then we traverse this array to find white spaces. We append the characters which are not the white spaces to StringBuffer object.

class RemoveWhiteSpaces
{
    public static void main(String[] args)
    {
        String str = " Core Java jsp servlet  jdbc struts hibernate spring ";
 
        //1. Using replaceAll() Method
 
        String strWithoutSpace = str.replaceAll("\\s", "");
 
        System.out.println(strWithoutSpace);         

Output : CoreJavajspservletsjdbcstrutshibernatespring
 
        //2. Without Using replaceAll() Method
 
        char[] strArray = str.toCharArray();
 
        StringBuffer sb = new StringBuffer();
 
        for (int i = 0; i < strArray.length; i++)
        {
            if( (strArray[i] != ' ') && (strArray[i] != '\t') )
            {
                sb.append(strArray[i]);
            }
        }
 
        System.out.println(sb);          

    }
}
//Output : CoreJavajspservletsjdbcstrutshibernatespring

There are two methods available in java to convert string to integer. One is Integer.parseInt() method and another one is Integer.valueOf() method. Both these methods are static methods of java.lang.Integer class. Both these methods throw NumberFormatException if input string is not a valid integer. The main difference between Integer.parseInt() and Integer.valueOf() method is that parseInt() method returns primitive int where as valueOf() method returns java.lang.Integer object.

public class Demo1
{
    public static void main(String[] args) 
    {
        String s = "2015";
         
        int i = Integer.parseInt(s);
         
        System.out.println(i);          
    }
}

//Output : 2015

Example2:
public class Demo2
{
    public static void main(String[] args) 
    {
        String s = "2015";
         
        int i = Integer.valueOf(s);
         
        System.out.println(i);          
    }
}
//Output : 2015

You are also often need to do the reverse conversion i.e converting from integer to string. Java provides couple of methods to do that also. one is Integer.toString() method and another one is String.valueOf() method. Both these methods return string representation of the given integer.

public class Demo1
{
    public static void main(String[] args) 
    {
        int i = 2015;
         
        String s = Integer.toString(i);
         
        System.out.println(s);     
    }
}

//Output : 2015

Example2:
public class Demo2
{
    public static void main(String[] args) 
    {
        int i = 2015;
         
        String s = String.valueOf(i);
         
        System.out.println(s);     
    }
}

//Output : 2015
KodNest reverse
public class MainClass1
{    
    static void reverseString(String inputString)
    {
        //Converting inputString to char array 'inputStringArray'
         
        char[] inputStringArray = inputString.toCharArray();
         
        //Defining a new char array 'resultArray' with same size as inputStringArray
         
        char[] resultArray = new char[inputStringArray.length];
         
        //First for loop : 
        //For every space in the 'inputStringArray', 
        //we insert spaces in the 'resultArray' at the corresponding positions 
         
        for (int i = 0; i < inputStringArray.length; i++) 
        {
            if (inputStringArray[i] == ' ') 
            {
                resultArray[i] = ' ';
            }
        }
         
        //Initializing 'j' with length of resultArray
         
        int j = resultArray.length-1;
                 
        //Second for loop :
        //we copy every non-space character of inputStringArray 
        //from first to last at 'j' position of resultArray
         
        for (int i = 0; i < inputStringArray.length; i++)
        {
            if (inputStringArray[i] != ' ') 
            {
                //If resultArray already has space at index j then decrementing 'j'
                 
                if(resultArray[j] == ' ')
                {
                    j--;
                }
                 
                resultArray[j] = inputStringArray[i];
                 
                j--;
            }
        }
         
        System.out.println(inputString+" ---> "+String.valueOf(resultArray));
    }
     
    public static void main(String[] args)
    {
        reverseString("I Am Not String");
         
        reverseString("JAVA JSP ANDROID");
         
      }
}
Output:

I Am Not String —> g ni rtS toNmAI
JAVA JSP ANDROID —> DIOR DNA PSJAVAJ

Input : kodnest for freshers

Output :todnesk  rof sresherf

Approach:As mentioned in the example we have to replace first and last character of word and keep rest of the alphabets as it is.

First we will create an Char array of given String by using toCharArray() method.

Now we iterate the char array by using for loop.

In for loop, we declare a variable whose value is dependent on i.

Whenever we found an alphabet we increase the value of i and whenever we reach at space, we are going to perform swapping between first and last character of the word which is previous of space.

class Demo 
{ 
    static String count(String str) 
    { 
        // Create an equivalent char array 
        // of given string 
        char[] ch = str.toCharArray(); 
        for (int i = 0; i < ch.length; i++) { 
  
            // k stores index of first character 
            // and i is going to store index of last  
            // character.  
            int k = i; 
            while (i < ch.length && ch[i] != ' ')  
                i++; 
              
            // Swapping 
            char temp = ch[k]; 
            ch[k] = ch[i - 1]; 
            ch[i - 1] = temp; 
  
            // We assume that there is only one space 
            // between two words. 
        } 
        return new String(ch); 
    }
 
    public static void main(String[] args) 
    { 
        String str = "kodnest for freshers"; 
        System.out.println(count(str)); 
    } 
}
public class StringReplace {
 
    public static void main(String args[]) {

     String word = "World";
    
     //replacing character in this String
     String replaced = word.replace("W", "K");
     System.out.println("Replacing character in String");
     System.out.println("Original String before replace : " + word);
     System.out.println("Replaced String : " + replaced);
    
     //replacing substring on String in Java    
     String str = "PHP is good programming language";
     replaced = str.replaceAll("PHP", "Java");
     System.out.println("String before replace : " + str);
     System.out.println("String after replace : " + replaced);
    
     //replacing all space in String with # using regular expression
     replaced = str.replaceFirst("\\s", "#");
     System.out.println("Replacing first match of regex using replaceFirst()");
     System.out.println("Original String before replacement : " + str);
     System.out.println("Final String : " + replaced);
    
     System.out.println("Replacing all occurrence of substring which match regex");
     replaced = str.replaceAll("\\s", "#");
     System.out.println("ReplaceAll Example : " + replaced);
    } 
   
}

Output:
Replacing character in String
Original String before replace : World
Replaced String : Korld
String before replace : PHP is good programming language
String after replace : Java is good programming language
Replacing first match of regex using replaceFirst()
Original String before replacement : PHP is good programming language
Final String : PHP#is good programming language
Replacing all occurrence of substring which match regex
ReplaceAll Example : PHP#is#good#programming#language
public class WordCount {  
      static int wordcount(String string)  
        {  
          int count=0;  
      
            char ch[]= new char[string.length()];     
            for(int i=0;i<string.length();i++)  
            {  
                ch[i]= string.charAt(i);  
                if( ((i>0)&&(ch[i]!=' ')&&(ch[i-1]==' ')) || ((ch[0]!=' ')&&(i==0)) )  
                    count++;  
            }  
            return count;  
        }  
      public static void main(String[] args) {  
          String string ="Java is a best programming language";  
         System.out.println(wordcount(string) + " words.");   
    }  
}  
Output:
6 words.
import java.util.Scanner;
class SwapTwoNumberWithoutThirdVariable
{
   public static void main(String args[])

   {
      int x, y;
      System.out.println("Enter the number for x and y ");
      Scanner in = new Scanner(System.in);
      x = in.nextInt();
      y = in.nextInt();

      System.out.println("Before Swapping\nx = "+x+"\ny = "+y);

      x = x + y
      y = x - y;
      x = x - y;

      System.out.println("After Swapping without third variable\nx = "+x+"\ny = "+y);

   }
}
Output:

Enter the number for x and y
25
49
Before Swapping
x = 25
y = 49
After Swapping without a third variable
x = 49
y = 25
class Loan
{
private int duration; //private variables examples of encapsulation
private String loan;
private String borrower;
private String salary;

//public constructor can break encapsulation instead use factory method
private Loan(int duration, String loan, String borrower, String salary)
{
this.duration = duration;
this.loan = loan;
this.borrower = borrower;
this.salary = salary;
}

// create loan can encapsulate loan creation logic
public Loan createLoan(String loanType)
{
return loan;
}
}

To achieve encapsulation in Java:

• Declare the variables of a class as ‘private’.

• Provide public setter and getter methods to modify and view the variable’s values

public class EncapTest
{
private String name;
private String idNum;
private int age;
public int getAge()
{
return age;
}
public String getName()
{
return name;
}
public String getIdNum()
{
return idNum;
}
public void setAge( int newAge)
{
age = newAge;
}
public void setName(String newName)
{
name = newName;
}

public void setIdNum( String newId)
{
idNum = newId;
}
}

$
$ $
$ $ $
$ $ $ $
$ $ $ $ $

public class Pattern {

    public static void main(String[] args) {
        int rows = 5;

        for(int i = 1; i <= rows; ++i) {
            for(int j = 1; j <= i; ++j) {
                System.out.print("$ ");
            }
            System.out.println();
        }
    }
}

1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

public class Pattern {

    public static void main(String[] args) {
        int rows = 5;

        for(int i = 1; i <= rows; ++i) {
            for(int j = 1; j <= i; ++j) {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

A
B B
C C C
D D D D
E E E E E

public class Pattern {

    public static void main(String[] args) {
        char last = 'E', alphabet = 'A';

        for(int i = 1; i <= (last-'A'+1); ++i) {
            for(int j = 1; j <= i; ++j) {
                System.out.print(alphabet + " ");
            }
            ++alphabet;

            System.out.println();
        }
    }
}

$ $ $ $ $
$ $ $ $
$ $ $
$ $
$

public class Pattern {

    public static void main(String[] args) {
        int rows = 5;

        for(int i = rows; i >= 1; --i) {
            for(int j = 1; j <= i; ++j) {
                System.out.print("$ ");
            }
            System.out.println();
        }
    }
}

1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

public class Pattern {

    public static void main(String[] args) {
        int rows = 5;

        for(int i = rows; i >= 1; --i) {
            for(int j = 1; j <= i; ++j) {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

$
$ $ $
$ $ $ $ $
$ $ $ $ $ $ $
$ $ $ $ $ $ $ $ $

public class Pattern {

    public static void main(String[] args) {
        int rows = 5, k = 0;

        for(int i = 1; i <= rows; ++i, k = 0) {
            for(int space = 1; space <= rows - i; ++space) {
                System.out.print("  ");
            }

            while(k != 2 * i - 1) {
                System.out.print("$ ");
                ++k;
            }

            System.out.println();
        }
    }
}

1
2 3 2
3 4 5 4 3
4 5 6 7 6 5 4
5 6 7 8 9 8 7 6 5

public class Pattern {

    public static void main(String[] args) {
        int rows = 5, k = 0, count = 0, count1 = 0;

        for(int i = 1; i <= rows; ++i) {
            for(int space = 1; space <= rows - i; ++space) {
                System.out.print("  ");
                ++count;
            }

            while(k != 2 * i - 1) {
                if (count <= rows - 1) {
                    System.out.print((i + k) + " ");
                    ++count;
                }
                else {
                    ++count1;
                    System.out.print((i + k - 2 * count1) + " ");
                }

                ++k;
            }
            count1 = count = k = 0;

            System.out.println();
        }
    }
}

1
1 1
1 2 1
1 3 3 1

public class Pattern {

    public static void main(String[] args) {
        int rows = 4, cof = 1;

        for(int i = 0; i < rows; i++) {
            for(int space = 1; space < rows - i; ++space) {
                System.out.print("  ");
            }

            for(int j = 0; j <= i; j++) {
                if (j == 0 || i == 0)
                    cof = 1;
                else
                    cof = cof * (i - j + 1) / j;

                System.out.printf("%4d", cof);
            }

            System.out.println();
        }
    }
}

1
2 3
4 5 6

public class Pattern {

    public static void main(String[] args) {
        int rows = 3, number = 1;

        for(int i = 1; i <= rows; i++) {

            for(int j = 1; j <= i; j++) {
                System.out.print(number + " ");
                ++number;
            }

            System.out.println();
        }
    }
}

1
2 2
3 3 3
4 4 4 4
5 5 5 5 5

import java.util.Scanner;
public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows ");

        int rows = sc.nextInt();
        
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(i + " ");
            }
            System.out.println();
        }
    }
}

1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows  ");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
        for (int i = rows; i >= 1; i--)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

1 2 3 4 5
1 2 3 4
1 2 3
1 2
1
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5

import java.util.Scanner;
public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows ");

        int rows = sc.nextInt();
        
        for (int i = rows; i >= 1; i--)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }

        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

5 4 3 2 1
4 3 2 1
3 2 1
2 1
1
1
2 1
3 2 1
4 3 2 1
5 4 3 2 1

import java.util.Scanner;
public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows ");

        int rows = sc.nextInt();

        for (int i = rows; i >= 1; i--)
        {
            for (int j = i; j >= 1; j--)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }

        for (int i = 1; i <= rows; i++)
        {
            for (int j = i; j >= 1; j--)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

5 4 3 2 1
5 4 3 2
5 4 3
5 4
5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows  ");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = rows; j >= i; j--)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

5
5 4
5 4 3
5 4 3 2
5 4 3 2 1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
                
        for (int i = rows; i >= 1; i--)
        {
            for (int j = rows; j >= i; j--)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

1
2 1
3 2 1
4 3 2 1
5 4 3 2 1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = i; j >= 1; j--)
            {
                System.out.print(j + " ");
            }
            System.out.println();
        }
    }
}

1
2 7
3 8 13
4 9 14 19
5 10 15 20 25

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            int temp = i;
            for (int j = i; j >= 1; j--)
            {
                System.out.print(temp + " ");
                temp = temp + rows;
            }
            System.out.println();
        }
    }
}

1
1 2 1
1 2 3 2 1
1 2 3 4 3 2 1
1 2 3 4 5 4 3 2 1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j + " ");
            }
            for (int k = i - 1; k >= 1; k--)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
    }
}

1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }
            for (int k = 1; k <= rows - i + 1; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
    }
}

1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = rows; j > i; j--)
            {
                System.out.print(" ");
            }

            for (int k = 1; k <= i; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(" ");
            }
            for (int k = 1; k <= rows - i; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
    }
}

12345
2345
345
45
5
5
45
345
2345
12345

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }

            for (int k = i; k <= rows; k++)
            {
                System.out.print(k);
            }
            System.out.println();
        }
        for (int i = rows; i >= 1; i--)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }

            for (int k = i; k <= rows; k++)
            {
                System.out.print(k);
            }
            System.out.println();
        }
    }
}

1 2 3 4 5
2 3 4 5
3 4 5
4 5
5
5
4 5
3 4 5
2 3 4 5
1 2 3 4 5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }

            for (int k = i; k <= rows; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
        for (int i = rows; i >= 1; i--)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }

            for (int k = i; k <= rows; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }

    }
}

5
4 5
3 4 5
2 3 4 5
1 2 3 4 5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = rows; i >= 1; i--)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print(" ");
            }

            for (int k = i; k <= rows; k++)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }

    }
}

1
1 0
1 0 1
1 0 1 0
1 0 1 0 1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j % 2 + " ");
            }

            System.out.println();
        }
    }
}

1 0 0 0 0
0 2 0 0 0
0 0 3 0 0
0 0 0 4 0
0 0 0 0 5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j < i; j++)
            {
                System.out.print("0 ");
            }
            System.out.print(i + " ");
            for (int k = i; k < rows; k++)
            {
                System.out.print("0 ");
            }
            System.out.println();
        }
    }
}

1 1 1 1 1
1 1 1 2 2
1 1 3 3 3
1 4 4 4 4
5 5 5 5 5

import java.util.Scanner;
public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = rows; j > i; j--)
            {
                System.out.print(1 + " ");
            }

            for (int k = 1; k <= i; k++)
            {
                System.out.print(i + " ");
            }
            System.out.println();
        }
    }
}

1 2 3 4 5 4 3 2 1
2 3 4 5 4 3 2
3 4 5 4 3
4 5 4
5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = i; j <= rows; j++)
            {
                System.out.print(j + " ");
            }
            for (int k = rows - 1; k >= i; k--)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
    }
}

1
2 2
3 3 3
4 4 4 4
5 5 5 5 5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            for (int j = rows; j > i; j--)
            {
                System.out.print(" ");
            }

            for (int k = 1; k <= i; k++)
            {
                System.out.print(i + " ");
            }
            System.out.println();
        }
    }
}

5 5 5 5 5
4 5 5 5 5
3 4 5 5 5
2 3 4 5 5
1 2 3 4 5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = rows; i >= 1; i--)
        {
            for (int j = i; j < rows; j++)
            {
                System.out.print(j + " ");
            }

            for (int k = rows - i; k < rows; k++)
            {
                System.out.print(5 + " ");
            }
            System.out.println();
        }
    }
}

1
2 6
3 7 10
4 8 11 13
5 9 12 14 15

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        int k = 1;
       
        for (int i = 1; i <= rows; i++)
        {
            k=i;
            for (int j = 1; j <= i; j++)
            {
                System.out.print(k + " ");
                k = k + rows - j; 
            }
            System.out.println();
        }
    }
}

1
2 4
3 6 9
4 8 12 16
5 10 15
6 12
7

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        int temp = 1;
        for(int i=1; i<=rows/2+1; i++)
        {
            for(int j=1;j<=i;j++)
            {
                System.out.print(temp*j+" ");
            }
            System.out.println();
            temp++;
        }
        for(int i=1; i<=rows/2; i++)
        {
            for(int j=1;j<=rows/2+1-i;j++)
            {
                System.out.print(temp*j+" ");
            }
            System.out.println();
            temp++;
        }
    }
}

1
2 9
3 8 10
4 7 11 14
5 6 12 13 15

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j <= i; j++)
            {
                if (j % 2 == 0)
                {
                    System.out.print(1 + j * rows - (j - 1) * j / 2 + i - j + " ");
                } else
                {
                    System.out.print(1 + j * rows - (j - 1) * j / 2 + rows - 1 - i + " ");
                }
            }

         System.out.println();
        }
    }
}

1 10 11 20 21
2 9 12 19 22
3 8 13 18 23
4 7 14 17 24
5 6 15 16 25

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 0; i < rows; i++)
        {
            for (int j = 0; j < rows; j++)
            {
                if (j % 2 == 0)
                    System.out.print((rows * (j)) + i + 1 + " ");
                else
                    System.out.print((rows * (j + 1)) - i + " ");
            }
            System.out.print("\n");
        }
    }
}

1
2 3
6 5 4
7 8 9 10
15 14 13 12 11

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args) 
    { 
        int curRow = 1;
        int counter = 1;
        
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);
        
        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i=1; i<= rows; i++)
        {
            if (i % 2 == 0) 
            {
                for (int j = 1; j<=i; j++)
                {
                    System.out.print(counter  +" ");
                    counter++;
                }
            }
            else
            {
                int reverse = curRow + counter - 1;
                for (int j = 0; j<i; j++)
                {
                    System.out.print(reverse--  +" ");
                    counter++;
                }
            }
            System.out.println();
            curRow++;
        }
    }
}

5 5 5 5 5
5 4 4 4 4
5 4 3 3 3
5 4 3 2 2
5 4 3 2 1

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        int temp = 0;
        for (int i = rows; i >= 1; i--)
        {
            for (int j = rows ; j >= i; j--)
            {
                System.out.print(j + " ");
                temp =j;
            }
            for (int k = rows - i+1; k < rows; k++)
            {
                System.out.print(temp + " ");
            }
            System.out.println();
        }
    }
}

5
4 5 4
3 4 5 4 3
2 3 4 5 4 3 2
1 2 3 4 5 4 3 2 1
2 3 4 5 4 3 2
3 4 5 4 3
4 5 4
5

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = rows; i >= 1; i--)
        {
            for (int j = i; j <= rows; j++)
            {
                System.out.print(j + " ");
            }
            for (int k = rows-1; k >= i; k--)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }

        for (int i = 2; i <= rows; i++)
        {
            for (int j = i; j <= rows; j++)
            {
                System.out.print(j + " ");
            }
            for (int k = rows-1; k >= i; k--)
            {
                System.out.print(k + " ");
            }
            System.out.println();
        }
    }
}

1 2 3 4 5
2 3 4 5 1
3 4 5 1 2
4 5 1 2 3
5 1 2 3 4

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
        
        for (int i = 1; i <= rows; i++)
        {
            int j = i;
            
            for (int k = 1; k <= rows; k++) 
            { 
                System.out.print(j + " "); 
                j++; 
                if (j > rows)
                    j = 1;
            }
            System.out.println();
        }
        sc.close();
    }
}

1 3 5 7 9
3 5 7 9 1
5 7 9 1 3
7 9 1 3 5
9 1 3 5 7

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();

        for (int i = 1; i <= rows; i++)
        {
            int j = (i * 2) - 1;

            for (int k = 1; k <= rows; k++) 
            { 
                System.out.print(j + " "); 
                j += 2; 
                if (j > (rows * 2) - 1)
                    j = 1;
            }
            System.out.println();
        }
        sc.close();
    }
}

1 1
12 21
123 321
1234 4321
1234554321

import java.util.Scanner;

public class Pattern
{
    public static void main(String[] args)
    {
        // Create a new Scanner object
        Scanner sc = new Scanner(System.in);

        // Get the number of rows from the user
        System.out.println("Enter the number of rows");

        int rows = sc.nextInt();
       
        for (int i = 1; i <= rows; i++)
        {
            for (int j = 1; j <= i; j++)
            {
                System.out.print(j);
            }
            
            for (int j= i*2 ; j < rows*2; j++) 
            { 
                System.out.print(" "); 
            } 
            for (int l = i; l >= 1; l--)
            {
                System.out.print(l);
            }
            System.out.println();
        }
        sc.close();
    }
}

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  1. Thank you Sir for providing us such a great learning application.

    1. Welcome Siban, Happy Learning!

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