class Demo{

    public int temp = 30;

}

public class T {  

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        Demo d1 = new Demo();

        d1.temp = 50;

        System.out.println("fun()方法调用之前："+d1.temp);

        fun(d1);

        System.out.println("fun()方法调用之后："+d1.temp);

    }

    public static void fun(Demo d2){

        d2.temp = 1000;

    }

}

public class T {  

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        String str1 = "hello";

        System.out.println("fun()方法调用之前："+str1);

        fun(str1);

        System.out.println("fun()方法调用之前："+str1);

    }

    public static void fun(String s2){

        s2 = "MLDN";

    }

}

class Demo{

    String temp = "hello";

}

public class T {  

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        Demo d1 = new Demo();

        d1.temp = "world";

        System.out.println("fun()方法调用之前："+d1.temp);

        fun(d1);

        System.out.println("fun()方法调用之后："+d1.temp);

    }

    public static void fun(Demo d2){

        d2.temp = "MLDN";

    }

}

原文地址：http://itmyhome.com/2015/03/java-study-notes-passed-by-reference