public class Thread10 {
    public static void main(String[] args) {
        Thread10_Entity entity = new Thread10_Entity();
        Thread10_1 t10_1 = new  Thread10_1(entity);
        t10_1.start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
 

            e.printStackTrace();
        }
        System.out.println(entity.get());

    }
}

class Thread10_1 extends Thread {
    private Thread10_Entity thread10_Entity;

    public Thread10_1(Thread10_Entity t10) {
        this.thread10_Entity = t10;
    }
    @Override
    public void run() {
        thread10_Entity.set
 
("admin", "admin");
    }
}
class Thread10_Entity {
    private String username = "user";
    private String password = "user";

    synchronized void set(String username, String password) {
        this.username = username;
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
 

            e.printStackTrace();
        }
        this.password = password;
    }
    String get() {
        return username + "   " + password;
    }
}

執行結果：admin user

加上sleep只是為了放大錯誤，便於觀察。
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那麼如何避免髒讀呢？上篇文章（ java併發程式設計學習之一段簡單程式碼證明synchronized鎖的是物件）中提到過，synchronized鎖的是物件，這裡就可以用上了。
在get方法上加上synchronized關鍵字即可，在set沒處理完之前，對物件加鎖，避免其他執行緒進行髒讀。