JAVA静态方法synchronized锁定类

面试的时候遇到一个问题，继承关系的静态方法是否可以覆写。

根据对JAVA语言的了解，静态方法是和类绑定的，因此不存在覆写，在运行时，继承关系应该是针对对象的，而不是类的。

具体的方式参考http://phl.iteye.com/blog/2029729

 

在这儿写一下多线程访问的时候锁定的状况。

 

public class child extends father {

	public synchronized static String call() throws InterruptedException {
		System.out.println("this is in child");
		Thread.sleep(10000);
		return "child";
	}
}

 

 

public class father {

	public synchronized static String call() throws InterruptedException{
		System.out.println("this is in father");
		Thread.sleep(10000);
		return "father";
	}
}

 

 

 

public class extendTest implements Callable<String> {

	private CountDownLatch begin;

	public extendTest(CountDownLatch begin) {
		this.begin = begin;
	}

	@Override
	public String call() throws Exception {
		try {
			begin.await();
			Random r = new Random();
			if (r.nextBoolean()) {
				return child.call();
			} else {
				return father.call();
			}

		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}
	
	public static void main(String args[]) throws InterruptedException, ExecutionException {
		CountDownLatch begin = new CountDownLatch(1);
		ExecutorService es = Executors.newFixedThreadPool(10);
		List<Future<String>> result = new ArrayList<Future<String>>();
		for (int i = 0; i < 10; i++) {
			extendTest et = new extendTest(begin);
			Future<String> r = es.submit(et);
			result.add(r);
		}
		begin.countDown();
		es.shutdown();

		for (Future<String> fs : result) {
			System.out.println(fs.get());
		}
	}
}

 

 

输出结果：

this is in child

this is in father

//停顿

this is in child

this is in father

//停顿

this is in child

child

child

father

this is in father

this is in child

father

this is in father

child

this is in child

child

father

this is in father

father

child

father

 

数据的返回结果说明形成了是一个在father类和child类上面的阻塞队列，排队进入锁块。

 

如有问题请留言。