How to display numbers with leading zeros

This program displays numbers with leading zeros.

Code:

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public class number {

        public static void main(String args[]) {
                long n = 123456789;
                String mask = "00000000000000";
                String ds = Long.toString(n);

                // double to string
                String z = mask.substring(0 , mask.length() - ds.length()) + ds;
                System.out.println(z);
      }
}

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This one too.

Code:

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public class Number {
public static void main(String args[]) {
    long n = 123456789;
    String f = "%014d";
    String z = String.format(f, n);
    System.out.println(z);
  }
}

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