Java Nested Loops with Examples (original) (raw)

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);
}

}

`