Java Data Type - 如何使用常量区域设置用法格式化数字

import java.text.NumberFormat;
import java.util.Locale;

public class Main {

  public static void main(String[] argv) {
    NumberFormat numberFormat = NumberFormat.getInstance();
    numberFormat.setParseIntegerOnly(false);
    double usersNumber = 197912.29;

    numberFormat = NumberFormat.getNumberInstance(Locale.US);
    System.out.println("User's number (US): "
        + numberFormat.format(usersNumber));
    numberFormat = NumberFormat.getNumberInstance(Locale.GERMANY);
    System.out.println("User's number (GERMANY): "
        + numberFormat.format(usersNumber));
    numberFormat = NumberFormat.getNumberInstance();
    System.out.println("User's number (DEFAULT LOCALE): "
        + numberFormat.format(usersNumber));
  }
}