引用傳遞

引用傳遞的核心意義：

同一塊堆內存空間能夠被不一樣的棧內存所指向，不一樣的棧內存能夠對同一個堆內存進行內容的修改。

 

實例1：

class Message {
    private int num = 10;
    
    public Message(int num){
        this.num = num;    //2.this是表明msg這個對象，num = 30
    }
    
    public void setNum(int num){
        this.num = num;
    }
    public int getNum(){
        return this.num;
    }
}

public class Demo{
    public static void main(String args[]){
        Message msg = new Message(30);    //1.實例化Massage對象msg
        fun(msg);    //3.調用fun方法
        System.out.println(msg.getNum());
    }
    
    public static void fun(Message temp){
        temp.setNum(100);    //4.temp是msg，調用Massage類的setNum方法，num=100
    }
}
/*--------------------------------------------------------------
E:\Javacode>java Demo
100

E:\Javacode>*/

 

實例2：

public class Demo{
    public static void main(String args[]){
        String msg = "hello";
        fun(msg);
        System.out.println(msg);
    }
    public static void fun(String temp){
        temp = "World";
    }
}
/*----------------------------------------------
E:\Javacode>java Demo
hello

E:\Javacode>*/

 

實例3：

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

public class Demo{
    public static void main(String args[]){
        
        Message msg = new Message("hello");
        fun(msg);
        System.out.println(msg.getInfo());
    }
    
    public static void fun(Message temp){
        temp.setInfo("world");
    }
}
/*------------------------------------------
E:\Javacode>java Demo
world

E:\Javacode>*/