在前文中提到，锁重入是支持继承的，但是同步其实不可以继承的
父类的方法是同步的：
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public class MyObject {
public synchronized void methodA() {
System.out.println("begin methodA threadName=" + Thread.currentThread().getName());
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("end methodA threadName=" + Thread.currentThread().getName());
}
}
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但是子类重写方法时去掉了 synchronized 关键字：
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public class MyObjectSon extends MyObject{
@Override
public void methodA() {
System.out.println("begin methodA threadName=" + Thread.currentThread().getName());
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("end methodA threadName=" + Thread.currentThread().getName());
}
}
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线程：
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public class ThreadA extends Thread {
private MyObject myObject;
public ThreadA(MyObject myObject) {
super();
this.myObject = myObject;
}
@Override
public void run() {
super.run();
myObject.methodA();
}
}
public class ThreadB extends Thread {
private MyObject myObject;
public ThreadB(MyObject myObject) {
super();
this.myObject = myObject;
}
@Override
public void run() {
super.run();
myObject.methodA();
}
}
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ThreadRunner:
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public class ThreadRunner {
public static void main(String[] args) {
MyObjectSon myObjectSon = new MyObjectSon();
ThreadA threadA = new ThreadA(myObjectSon);
threadA.setName("A");
ThreadB threadB = new ThreadB(myObjectSon);
threadB.setName("B");
threadA.start();
threadB.start();
}
}
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控制台：
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begin methodA threadName=A
begin methodA threadName=B
end methodA threadName=A
end methodA threadName=B
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子类的方法经过重写，已经不具备同步了
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