Android 上的 Java 并发

Question

我正在尝试制作一个演示并发问题的 Android 应用程序示例，但令我感到奇怪的是，我的代码显示了正确的结果，而不是竞争条件导致的错误结果。以下是我的代码，我读过 think in Java(大约 1150 页)

    import android.os.Bundle;
    import android.app.Activity;
    import android.util.Log;
    import android.view.Menu;

public class MainActivity extends Activity {
    private breadBaker bB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("shanwu","Thread Test Starts!");
        bB = new breadBaker();
        bB.makeBread();
        breadBuyer TA = new breadBuyer();
            try{
                Thread a =new Thread(TA); 
                Thread b =new Thread(TA); 
                Thread c =new Thread(TA); 
                Thread d =new Thread(TA); 
                Thread e =new Thread(TA);
                Thread f =new Thread(TA);
                Thread g =new Thread(TA);
                Thread h =new Thread(TA);
                Thread i =new Thread(TA);
                Thread j =new Thread(TA);
                a.start();
                b.start();
                c.start();
                d.start();
                e.start();
                f.start();
                g.start();
                h.start();
                i.start();
                j.start();
                bB.makeBread();
                }catch(Exception e){
                    e.printStackTrace();
                }
        }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    class breadBaker{
        private int breadCount;
        public breadBaker(){
            breadCount = 3;
        }
        public void makeBread(){
            breadCount++;
            Log.d("shanwu","make one bread, current bread count: "+breadCount);
        }
        public void giveBread(){
            breadCount--;
            Log.d("shanwu","sold one bread, current bread count: "+breadCount);
        }
        public int getBreadCount()
        {
            return breadCount;
        }
    }

    class breadBuyer implements Runnable{
        public void buyBread(){
            bB.giveBread();
        }
        public void waitInLine(){
　　　　　　　　　　// Thread.Sleep(100);
        }
        @Override
        public void run() {
            // TODO Auto-generated method stub
            if(bB.getBreadCount() > 0){
                buyBread();
            }
            else
            {
                waitInLine();
            }
        }
    }
}

我基本上是从 Think in Java 的内容中学习，并尝试让它在 Android 上运行...请指出似乎是什么问题，我认为 breadCount 会由于竞争条件而变为负值，但事实并非如此, 它工作正常......

Answer 1

又看了一遍Concurrency从头开始的书，说demo代码很难出错，但是还是要注意concurrency问题，不然后面会出事的。