JAVA NESTED FOR LOOP

What are Nested For loops in Java ?

Nested For Loop in Java consists of nested loops i.e one loop inside another. Once outer loop executes then execution of inner loop happens completely. These nested loops are very important in pattern programs and these pattern problems are one of the hot topic of interviews.

for(statement; condition check; increment/decrement) {// Code inside outer loop 
for(statement; condition check; increment/decrement) {// Code inside inner loop }
// Code inside outer loop }

Note : In place of for loop you can use any loop. Nesting of loops can be done with any combination of loops i.e you can out for loop inside the body of while loop.

As soon as you enter inside the body of outer loop, inner loop executes completely. Now in the next module we will see few examples related to nesting for for loops in Java.

Example: Nested For Loop in Java

If you still dont know the implementation of a single for loop in java then kindly go through Java for loops tutorial.

Example 1: Nested for loop

// Java program to demonstrate nested for loop example
import java.util.*;
public class NestedLoopExample{
    public static void main(String args[]){  
        Scanner sc= new Scanner(System.in); 
        System.out.print("Enter the outer loop iteration value : ");
        int outer= sc.nextInt(); 

        System.out.print("Enter the inner loop iteration value : ");
        int inner= sc.nextInt(); 

        for(int i = 1 ; i <= outer ; i++ ) {
            System.out.println("Iteration : " + i);
            for(int j = 1; j <= inner; j++) {
                System.out.println("Best Java Tutorials");
             }
         }
    }
}

Dry Run

In this example we have taken the inputs as 3 and 2. Kindly give different values for i and j and then dry run your program with pen and paper to understand the flow.

Example: Java Pattern Program

In this example we will create a pattern with the help of Java nested for loops.

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Example 1: Right Triangle Star Pattern

// Java program to create a Right Triangle Star Pattern Program
import java.util.*;
public class NestedLoopExample{
    public static void main(String args[]){  
        Scanner sc= new Scanner(System.in); 
        System.out.print("Enter the height : ");
        int height= sc.nextInt(); 

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

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Dry Run

Its time to learn while loop in Java . Switch on to the next tutorial.