原因是,当线程t1锁定静态对象firstData时,他已经获得了对类的锁定.因此,当他试图锁定另一个静态对象secondData时,请求应该阻塞.
但是,程序运行正常并打印***成功获得了两个锁
锁定静态对象的原因是什么？
public class Deadlock {
public static void main(String[] args) {
Thread t1 = new Thread(new DeadlockRunnable());
t1.start();
}
}
class DeadlockRunnable implements Runnable {
static Object firstData = new Object();
static Object secondData = new Object();
public void run() {
synchronized(firstData) {
synchronized(secondData) {
System.out.println("*** Successfully acquired both the locks");
}
}
}
}
对于那些回答锁是对象而不是课堂的人,请看一下this
解决方法
The reason being,when thread t1 locks static object firstData,he has acquired a lock on the class.
锁定静态对象仅锁定该对象,而不是类.您正在锁定两个单独的对象.
question you refered to大约是synchronized methods而不是synchronized statements.这两个相关结构的工作方式略有不同.
其次,即使您锁定了同一个对象,您的代码仍然不会死锁(ideone).内在锁是可重入的.这意味着如果线程尝试两次使用相同的锁,则线程不会自行死锁.
Reentrant Synchronization
Recall that a thread cannot acquire a lock owned by another thread. But a thread can acquire a lock that it already owns. Allowing a thread to acquire the same lock more than once enables reentrant synchronization. This describes a situation where synchronized code,directly or indirectly,invokes a method that also contains synchronized code,and both sets of code use the same lock. Without reentrant synchronization,synchronized code would have to take many additional precautions to avoid having a thread cause itself to block.
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