synchronized依靠锁机制实现多线程的同步，锁分两种
- 对象锁
- 类锁
1.synchronized作用于普通方法时依靠对象锁工作，多线程访问synchronized方法，一旦某个线程抢到锁后，其他进程排队等待
等效于
示例：
方法method2会一直等待method1执行完成后再执行。
synchronized void method(){}整个函数加上synchronized块，效率并不好。
2.synchronized作用于静态方法相当于
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Java多线程synchronized
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void method{
synchronized(this){
}
}
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public class TestSynchronized {
public synchronized void method1() throws InterruptedException {
System.out.println("Method1 start at :" + System.currentTimeMillis());
Thread.sleep(6000);
System.out.println("Method1 end at :" + System.currentTimeMillis());
}
public synchronized void method2() throws InterruptedException {
while (true) {
System.out.println("method2 running");
Thread.sleep(200);
}
}
static TestSynchronized instance = new TestSynchronized();
public static void main(String[] args) {
Thread thread1 = new Thread(new Runnable() {
@Override
public void run() {
try {
instance.method1();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
for (int i = 1; i < 4; i++) {
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Thread1 still alive");
}
}
});
Thread thread2 = new Thread(new Runnable() {
@Override
public void run() {
try {
instance.method2();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
thread1.start();
thread2.start();
}
}