Java Nested Loops with Examples

Last Updated : 11 Jan, 2024

A Nested loop means a loop statement inside another loop statement. That is why nested loops are also called "loop inside loop".

Nested For loop

for ( initialization; condition; increment ) {
for ( initialization; condition; increment ) {
// statement of inside loop
}

// statement of outer loop
}

Nested While loop

while(condition) {
while(condition) {
// statement of inside loop
}

// statement of outer loop
}

Nested Do-While loop

do{
do{
// statement of inside loop
}
while(condition);

// statement of outer loop
}
while(condition);

Note: There is no rule that a loop must be nested inside its own type. In fact, there can be any type of loop nested inside any type and to any level.

Hybrid Java Nested Loops

do{
while(condition) {
for ( initialization; condition; increment ) {
// statement of inside for loop
}

// statement of inside while loop

}

// statement of outer do-while loop
}while(condition);

Below are some examples to demonstrate the use of Nested Loops:

Examples of Java Nested Loops

Example 1: Below program uses a nested for loop to print a 2D matrix.

Java

// Java program to print the elements of // a 2 D array or matrix import java.io.*; // Driver Class class GFG {  public static void print2D(int mat[][])  {  // Loop through all rows  for (int i = 0; i < mat.length; i++) {  // Loop through all elements of current row  for (int j = 0; j < mat[i].length; j++)  System.out.print(mat[i][j] + " ");  System.out.println();  }  }    // main function  public static void main(String args[]) throws IOException  {  int mat[][] = { { 1, 2, 3, 4 },  { 5, 6, 7, 8 },  { 9, 10, 11, 12 } };  print2D(mat);  } }

Output

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

Example 2: Below program uses a nested for loop to print all prime factors of a number.

Java

// Java program to print all prime factors import java.io.*; import java.lang.Math; // Driver Class class GFG {  // A function to print all prime factors  // of a given number n  public static void primeFactors(int n)  {  // Print the number of 2s that divide n  while (n % 2 == 0) {  System.out.print(2 + " ");  n /= 2;  }  // n must be odd at this point. So we can  // skip one element (Note i = i +2)  for (int i = 3; i <= Math.sqrt(n); i += 2) {  // While i divides n, print i and divide n  while (n % i == 0) {  System.out.print(i + " ");  n /= i;  }  }  // This condition is to handle the case when  // n is a prime number greater than 2  if (n > 2)  System.out.print(n);  }  // main function  public static void main(String[] args)  {  int n = 315;  primeFactors(n);  } }