How do I add leading zeros to a number?

This example shows you how to use the String.format() method to add zero padding to a number. If you just want to print out the result you can use System.out.format(). This method is available since Java 1.5, so If you use a previous version you can use the NumberFormat class, see: How do I format a number with leading zeros?.

package org.kodejava.lang;

public class LeadingZerosExample {
    public static void main(String[] args) {
        int number = 1500;

        // String format below will add leading zeros (the %0 syntax)
        // to the number above. The length of the formatted string will
        // be 7 characters.
        String formatted = String.format("%07d", number);

        System.out.println("Number with leading zeros: " + formatted);
    }
}

Here is the result of the code snippet above:

Number with leading zeros: 0001500

For more information about the format syntax you can find it here.