Java Data Type - 如何为数字添加前导零

import java.text.DecimalFormat;
import java.text.NumberFormat;

public class Main {
  public static void main(String[] args) {
    int areaCode = 123;
    int exchangeCode = 456;

    NumberFormat nf3 = new DecimalFormat("0000");

    System.out.println(nf3.format(areaCode) + "-" + nf3.format(exchangeCode));
  }

}