class Sync {
private byte[] lock = new byte[0];
public void sync() throws InterruptedException {
synchronized (lock) {
runThread();
}
}
public void thisSync() throws InterruptedException {
synchronized (this) {
runThread();
}
}
public synchronized static void staticSync() throws InterruptedException { // 同步的static 函数
runThread();
}
public void classSync() throws InterruptedException { //
synchronized (Sync.class) {
runThread();
}
}
private static void runThread() throws InterruptedException {
Thread current = Thread.currentThread();
System.out.println("current thread id:" + current.getId() + "enter...");
System.out.println("1111");
Thread.sleep(1000);
System.out.println("2222");
Thread.sleep(1000);
System.out.println("3333");
Thread.sleep(1000);
System.out.println("4444");
Thread.sleep(1000);
System.out.println("5555");
System.out.println("current thread id:" + current.getId() + "out...");
}
}
1.同一个线程lock对象锁是否可复用（即不用等待）
结论：可复用
public class TestObjectSyncLock {
private static byte[] lock = new byte[0];//零长度的byte数组对象创建起来将比任何对象都经济――查看编译后的字节码：生成零长度的byte[]对象只需3条操作码，而Object lock = new Object()则需要7行操作码。
public static void main(String[] args) throws InterruptedException {
//1.同一个线程lock对象锁是否可复用（即不用等待）----可复用
synchronized (lock) {
new Thread(new Runnable() {
public void run() {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("aaa");
}
}).start();
// lock.notify();
}
synchronized (lock) {
System.out.println("bbb");
// lock.wait();
}
}
}
结果：
bbb
aaa
2.同一个对象，多线程访问(一个主线程，一个新开线程)
结论：锁有效
Thread current = Thread.currentThread();
System.out.println("current thread id:"+current.getId()+"start...");
final Sync sync =new Sync();
new Thread(new Runnable() {
public void run() {
Thread current = Thread.currentThread();
System.out.println("current thread id:"+current.getId()+"start...");
try {
sync.sync();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
sync.sync();
结果：
current thread id:1start...
current thread id:1enter...
1111
current thread id:9start...
2222
3333
4444
5555
current thread id:1out...
current thread id:9enter...
1111
2222
3333
4444
5555
current thread id:9out...
3.不同对象，多线程访问
结论：锁无效
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
final Sync sync = new Sync();
final Sync sync2 = new Sync();
new Thread(new Runnable() {
public void run() {
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
try {
sync2.sync();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
sync.sync();
结果：
currret thread id:1start...
current thread id:1enter...
1111
currret thread id:9start...
current thread id:9enter...
1111
2222
2222
3333
3333
4444
4444
5555
current thread id:1out...
5555
current thread id:9out...
4.wait(),notify()----调用wait或notify时，该线程必须是该对象锁的所有者,否则会抛出Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
new Thread(new Runnable() {
public void run() {
System.out.println("------");
synchronized (lock) {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
lock.notify();
System.out.println(" after notify ...");
}
}
}).start();
synchronized (lock) {
System.out.println("enter ...");
lock.wait();
System.out.println("out ...");
}
结果：
enter ...
------
after notify ...
out ...
5.wait(),notifyAll()----notifyAll()唤醒所有正在wait的不同线程
new Thread(new Runnable() {
public void run() {
synchronized (lock) {
System.out.println("enter thread 1 ...");
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("leave thread 1 ...");
}
}
}).start();
new Thread(new Runnable() {
public void run() {
synchronized (lock) {
System.out.println("enter thread 2 ...");
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("leave thread 2 ...");
}
}
}).start();
new Thread(new Runnable() {
public void run() {
System.out.println("------");
synchronized (lock) {
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
lock.notifyAll();// notifyAll方法会唤醒所有正在等待对象控制权的线程。
// lock.notify();//随机通知一个正在等待的线程
System.out.println("after notifyAll ...");
}
}
}).start();
结果：
enter thread 1 ...
enter thread 2 ...
------
after notifyAll ...
leave thread 2 ...
leave thread 1 ...
6.static 同步方法,不同对象
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
Sync sync = new Sync();
new Thread(new Runnable() {
public void run() {
Sync sync = new Sync();
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
try {
sync.staticSync();// 锁有效
// Sync.staticSync();//锁有效
// sync.sync();//锁无效
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
sync.staticSync();// 锁有效
// Sync.staticSync();//锁有效
// sync.sync();//锁无效
结果：
currret thread id:1start...
current thread id:1enter...
1111
currret thread id:9start...
2222
3333
4444
5555
current thread id:1out...
current thread id:9enter...
1111
2222
3333
4444
5555
current thread id:9out...
7.class 同步方法,不同对象
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
Sync sync = new Sync();
new Thread(new Runnable() {
public void run() {
Sync sync = new Sync();
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
try {
sync.classSync();// 锁有效
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
sync.classSync();// 锁有效
结果：
currret thread id:1start...
current thread id:1enter...
1111
currret thread id:9start...
2222
3333
4444
5555
current thread id:1out...
current thread id:9enter...
1111
2222
3333
4444
5555
current thread id:9out...
8.this 同步方法,不同对象,跟2一样，对象锁
final Sync sync = new Sync();
new Thread(new Runnable() {
public void run() {
// Sync sync =new Sync();
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
try {
sync.thisSync();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
new Thread(new Runnable() {
public void run() {
// Sync sync =new Sync();
Thread current = Thread.currentThread();
System.out.println("currret thread id:" + current.getId() + "start...");
try {
sync.thisSync();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
结果：
currret thread id:9start...
current thread id:9enter...
1111
currret thread id:10start...
2222
3333
4444
5555
current thread id:9out...
current thread id:10enter...
1111
2222
3333
4444
5555
current thread id:10out...