Java中的值传递和引用传递

当一个变量最为一个参数传入方法内部的时候，会有两种不同的传递方式：值传递和引用传递。

值传递的特点：不管方法内部对传进去的参数作任何改变，也不会影响方法外部的变量的值

引用传递的特点：方法内部对传进去的参数作的改变也会影响方法外部的变量的值

那么哪些是值传递，哪些是引用传递呢？

基本类型（8种）的传递都是值传递
引用类型（除String外）都是引用传递
Strng比较特殊，它虽然是引用类型，但是却是值传递

通过一下例子来理解：

Student.java

[java]
package com.tianjf;

public class Student {
    private String name;

    public Student(String name) {
        super();
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return name;
    }
}
package com.tianjf;

public class Student {
private String name;

public Student(String name) {
super();
this.name = name;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

@Override
public String toString() {
return name;
}
}
Test.java

[java]
package com.tianjf;

public class Test {

    private static void changeInt(int i) {
        i = 1;
    }

    private static void changeStudent(Student student) {
        student.setName("李四");
    }

    private static void changeString(String str) {
        str = "456";
    }

    public static void main(String[] args) {
        int i = 0;
        String str = "123";
        Student student = new Student("张三");
        System.out.println("Before change:\ni：" + i + "\n" + "student:" + student.toString() + "\n" + "str:" + str);

        changeInt(i);
        changeStudent(student);
        changeString(str);
        System.out.println("After change:\ni：" + i + "\n" + "student:" + student.toString() + "\n" + "str:" + str);
    }
}
package com.tianjf;

public class Test {

private static void changeInt(int i) {
  i = 1;
}

private static void changeStudent(Student student) {
  student.setName("李四");
}

private static void changeString(String str) {
  str = "456";
}

public static void main(String[] args) {
  int i = 0;
  String str = "123";
  Student student = new Student("张三");
  System.out.println("Before change:\ni：" + i + "\n" + "student:" + student.toString() + "\n" + "str:" + str);

  changeInt(i);
  changeStudent(student);
  changeString(str);
  System.out.println("After change:\ni：" + i + "\n" + "student:" + student.toString() + "\n" + "str:" + str);
}
}
运行结果： www.zzzyk.com

Before change:
i：0
student:张三
str:123
After change:
i：0
student:李四
str:123

从运行结果可以看出，int和String类型的值经过change方法后没有变，而student的值变了。

作者：tianjf0514

补充：软件开发 , Java ,