Java Pass By Value Example

package author.estone.java;

import java.util.Date;

public class PassByValue {

	public static void main(String[] args) {

		Date d1 = new Date("1 Apr 98");
		nextDateUpdate(d1);
		System.out.println("d1 after nextDay: " + d1);// date的值已被修改

		Date d2 = new Date("1 Apr 98");
		nextDateReplace(d2);
		System.out.println("d2 after nextDay: " + d2);// date的值没有被修改

	}

	private static void nextDateUpdate(Date arg) {
		arg.setDate(arg.getDate() + 1);
		System.out.println("arg in nextDay: " + arg);
	}

	private static void nextDateReplace(Date arg) {
		arg = new Date(arg.getYear(), arg.getMonth(), arg.getDate() + 1);
		System.out.println("arg in nextDay: " + arg);
	}

}

Console Output：

arg in nextDay: Thu Apr 02 00:00:00 CST 1998
d1 after nextDay: Thu Apr 02 00:00:00 CST 1998
arg in nextDay: Thu Apr 02 00:00:00 CST 1998
d2 after nextDay: Wed Apr 01 00:00:00 CST 1998

 

This code is from the book 《Refactoring》.