Java Data Type - 如何使用java.text.NumberFormat格式化货币值

import java.text.NumberFormat;

public class Main {
  public static void main(String[] argv) throws Exception {

    NumberFormat nf = NumberFormat.getCurrencyInstance();

    System.out.println("currency format: " + nf.format(1234.56) + " "
        + nf.format(-1234.56));
  }
}