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 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);
}
} |
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Example 2: Below program uses a nested for loop to print all prime factors of a number.
// 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);
}
} |
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