Java传值 传址

1.测试代码：传递String

public class MyProject
{
    public static void main(String[] agrs) {

        String name = "haha";
        System.out.println("before change : " + name);
        change(name);
        System.out.println("after change : " + name);
    }

    private static void change(String s) {
        s = "changed";
    }
}

测试结果

before change : haha
after change : haha

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2.测试代码：传递对象-修改对象信息

public class MyProject
{
    public static void main(String[] agrs) {

        Student mStudent = new Student("xiaohong", 10);
        System.out.println("before change : " + mStudent.getName() + " " + mStudent.getAge());
        change(mStudent);
        System.out.println("after change : " + mStudent.getName() + " " + mStudent.getAge());
    }

    private static void change(Student s) {
        s.setName("xiaoming");
        s.setAge(15);
    }
}

测试结果

before change : xiaohong 10
after change : xiaoming 15

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3.测试代码：传递对象-修改对象指向

public class MyProject
{
    public static void main(String[] agrs) {

        Student mStudent = new Student("xiaohong", 10);
        System.out.println("before change : " + mStudent.getName() + " " + mStudent.getAge());
        change(mStudent);
        System.out.println("after change : " + mStudent.getName() + " " + mStudent.getAge());
    }

    private static void change(Student s) {
        s = new Student("xiaoming", 15);
    }
}

测试结果

before change : xiaohong 10
after change : xiaohong 10