[問題] 物件與多執行緒的問題

[zheng2010 (自我催眠)]

各位前輩們好，

在下面那簡單的程式碼中

s會重複被assign，所以

我預期的輸出結果是

s1=this is obj1
s2=this is obj2
s2=this is obj2 <--- Main can Access
s2=this is obj2 <--- Main can Access
s2=this is obj2 <--- Main can Access
s2=this is obj2 <--- Main can Access
s2=this is obj2 <--- Main can Access
s2=this is obj2 <--- Main can Access

但是因為字串是由thread來印的

所以實際上的輸出如下

s1=this is obj1
s2=this is obj2
s1=this is obj1
s2=this is obj2 <--- Main can Access
s1=this is obj1
s2=this is obj2 <--- Main can Access
s1=this is obj1
s2=this is obj2 <--- Main can Access
s1=this is obj1
s2=this is obj2 <--- Main can Access

也就是說第一個物件還是存在著?

照理說不是進行第二次的s = new CAR("s2=this is obj2")後

GC就會去把access不到的記憶體清掉嗎，那為什麼還是會一直印出s1=.....

還是說是因為thread的關係?(thread 負責印出字串)


謝謝


---------------程式碼-----------------------------

public class Game{
         static CAR s;
     public static void main(String []args){
                s = new CAR("s1=this is obj1");
                s = new CAR("s2=this is obj2");
                try{
                    Thread.sleep(2000);
                   }catch(Exception e)
                   {
                   }
                s.x+=" <--- Main can Access";
     }
}

class CAR {
    CAR(String s)
    {
        x=s;
        Thread thread1 = new Thread(aa);
        thread1.start();
    }
    public String x;
    private Runnable aa= new Runnable(){

        @Override
                public void run() {
                while(true)
                {
                System.out.println(x);
                try{
                Thread.sleep(1000);
                }catch(Exception e)
                {

                }
            }
                }//run
        };
}

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◆ From: 114.35.228.73
推 PsMonkey:只是 s 沒有指向第一個 car，不代表第一個 car 沒人 ref
推 Elohim123:乍看起來是因為每次在做new CAR()時constructor裡面
→ Elohim123:都會去做thread1.start()這樣 ?
→ zheng2010:可是thread1也是物件的一部分，所以物件自己ref自己?
→ asilzheng:沒說過 GC 會馬上動作吧?
推 PsMonkey:看一下 Thread.init() 吧
→ zheng2010:回a大 如果第一個car還有人ref  GC應該就不會清掉它吧?
→ cha122977:還有人ref阿 不然怎麼印出來的?