JAVA基础学习之路（十一）引用传递

 引用传递：

不同栈内存可以指向同一块堆内存，不同栈内存可以对一块堆内存进行修改

范例一：

class Message {
    private int num = 10;
    public Message(int num) {
        this.num = num;
    }
    public void setNum(int num) {
        this.num = num;
    }
    public int getNum() {
        return this.num;
    }
} 

public class test1 {
    public static void main(String args[]) {
        Message msg = new Message(30);
        fun(msg);//引用传递
        System.out.println(msg.getNum());
    }    
    public static void fun(Message temp) {
        temp.setNum(100);
    }
}
//输出  100

内存分析：

范例二：

public class test1 {
    public static void main(String args[]) {
        String msg = "hello";
        fun(msg);//引用传递
        System.out.println(msg);
    }    
    public static void fun(String temp) {
        temp = "world";
    }
}//输出：hello

输出结果仍为hello，msg的值没有被改变

原因：String类对象的内容一旦声明，则不可改变。对象内容的改变，依靠的是引用地址的改变

范例三：

class Message {
    private String info = "nihao";
    public Message(String info) {
        this.info = info;
    }
    public void setInfo(String info) {
        this.info = info;
    }
    public String getInfo() {
        return this.info ;
    }
} 

public class test1 {
    public static void main(String args[]) {
        Message msg = new Message("hello");
        fun(msg);//引用传递
        System.out.println(msg.getInfo());
    }    
    public static void fun(Message temp) {
        temp.setInfo("world");
    }
}//输出world

内存分析：

class Member {
    private int mid;
    private String name;
    private Member child;
    private Car car;
    public Member(int mid, String name) {
        this.mid = mid;
        this.name = name;
    }
    public String getInfo() {
        return "编号:"+this.mid+"
"+
                "名字"+this.name;    
    }
    public void setCar(Car car) {
        this.car = car;    
    }
    public Car getCar() {
        return this.car;    
    }
    public void setChild(Member child) {
        this.child = child;
    }
    public Member getChild() {
        return this.child;
    }
}

class Car {
    private Member member;
    private String name;
    public Car(String name) {
        this.name = name;
    }
    public String getInfo() {
        return "车的名字"+name;
    }
    public void setMember(Member member) {
        this.member = member;
    }
    public Member getMember() {
        return this.member;
    }
}

public class test1 {
    public static void main(String args[]) {
        Member m = new Member(1,"张三");
        Member ch = new Member(2,"李四");
        Car c = new Car("宝马");
        Car cc = new Car("奔驰");
            
        m.setCar(c);
        c.setMember(m);
        
        ch.setCar(cc);
        cc.setMember(ch);
        m.setChild(ch);
        
        System.out.println(m.getCar().getInfo());
        System.out.println(c.getMember().getInfo());
        System.out.println(m.getChild().getCar().getInfo());
    }    
}