For Loop

Examples:

1) Program to print Even Numbers:

/*
	List Even Numbers Java Example
	This List Even Numbers Java Example shows how to find and list even
	numbers between 1 and any given number.
*/
 
public class ListEvenNumbers {
 
	public static void main(String[] args) {
		
		//define limit
		int limit = 50;
		
		System.out.println("Printing Even numbers between 1 and " + limit);
		
		for(int i=1; i <= limit; i++){
			
			// if the number is divisible by 2 then it is even
			if( i % 2 == 0){
				System.out.print(i + " ");
			}
		}
	}
}
 
/*
Output of List Even Numbers Java Example would be
Printing Even numbers between 1 and 50
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 
*/

2) Program to find the sum of natural numbers from 1 to 1000.

// Program to find the sum of natural numbers from 1 to 1000.

class Number {
   public static void main(String[] args) {
      
      int sum = 0;
	   
      for (int i = 1; i <= 1000; ++i) {
         sum += i;     // sum = sum + i
      }
	   
      System.out.println("Sum = " + sum);
   }
}

When you run the program, the output will be:

Sum = 500500

Here, the variable sum is initialized to 0. Then, in each iteration of for loop, variable sum is assigned sum + i and the value of i is increased until i is greater than 1000. For better visualization,

1st iteration: sum = 0+1 = 1
2nd iteration: sum = 1+2 = 3
3rd iteration: sum = 3+3 = 6
4th iteration: sum = 6+4 = 10
... .. ...

999th iteration: sum = 498501 + 999 = 499500
1000th iteration: sum = 499500 + 1000 = 500500

Nested For Loop:

package com.test.test1;

public class Clock {
	public static void main(String[] args) {
		for (int hrs = 1; hrs <= 6; hrs++) {
			for (int min = 1; min <= 60; min++) {
				System.out.println(hrs + ":" + min);
			}
		}
	}
}

Example 1: Program to create a pattern

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

Here is a program to create the above pattern using nested loops.

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("");
      }
   }
}

Example 2: Program to create a pattern

*
* *
* * *
* * * *

Here is a program to create the above pattern using nested loops.

class Pattern {
   public static void main(String[] args) {
      
      int rows = 4;
      
      for(int i = 1; i <= rows; ++i)
      {
          for(int j = 1; j <= i; ++j)
          {
             System.out.print("*" + " ");
          }
          System.out.println("");
      }
   }
}

Example 3: Program to create a pattern

*****
****
***
**
*

/*
	Java Pyramid 2 Example
	This Java Pyramid example shows how to generate pyramid or triangle like
	given below using for loop.
	
	*****
	****
	***
	**
	*
*/
 
public class JavaPyramid2 {
 
	public static void main(String[] args) {
		
		for(int i=5; i>0 ;i--){
			
			for(int j=0; j < i; j++){
				System.out.print("*");
			}
			
			//generate a new line
			System.out.println("");
		}
	}
}
 
/*
 
Output of the example would be
*****
****
***
**
*
 
*/

Problems:

1) WAP to print Odd Numbers.

2) WAP to draw the below patterm.

*
**
***
****
*****
*****
****
***
**
*

3) WAP to draw the below pattern.

        *
      * * *
    * * * * *
  * * * * * * *
* * * * * * * * *

4) WAP to draw the below pattern.

* * * * * * * * *
  * * * * * * *
    * * * * *
      * * *
        *