java integer to string with leading zeros

/**
 * @author lautturi.com 
 * Java example: padding a string to a certain length with zero on the left in java
 */

import java.util.*;

public class Lautturi {
    
	public static void main(String[] args) {

		Integer num = 123;

		String str = String.format("%16s", Integer.toString(num)).replace(' ', '0');
		
		System.out.println(str);

	}
}

output:

0000000000000123