Lock是一个接口，为了使用一个Lock对象，需要用到
Lock lock = new ReentrantLock();
与 synchronized (someObject) 类似的，lock()方法，表示当前线程占用lock对象，一旦占用，其他线程就不能占用了。
与 synchronized 不同的是，一旦synchronized 块结束，就会自动释放对someObject的占用。 lock却必须调用unlock方法进行手动释放，为了保证释放的执行，往往会把unlock() 放在finally中进行。
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package
multiplethread;
import
java.text.SimpleDateFormat;
import
java.util.Date;
import
java.util.concurrent.locks.Lock;
import
java.util.concurrent.locks.ReentrantLock;
public
class
TestThread {
public
static
String now() {
return
new
SimpleDateFormat(
"HH:mm:ss"
).format(
new
Date());
}
public
static
void
log(String msg) {
System.out.printf(
"%s %s %s %n"
, now() , Thread.currentThread().getName() , msg);
}
public
static
void
main(String[] args) {
Lock lock =
new
ReentrantLock();
Thread t1 =
new
Thread() {
public
void
run() {
try
{
log(
"线程启动"
);
log(
"试图占有对象：lock"
);
lock.lock();
log(
"占有对象：lock"
);
log(
"进行5秒的业务操作"
);
Thread.sleep(
5000
);
}
catch
(InterruptedException e) {
e.printStackTrace();
}
finally
{
log(
"释放对象：lock"
);
lock.unlock();
}
log(
"线程结束"
);
}
};
t1.setName(
"t1"
);
t1.start();
try
{
//先让t1飞2秒
Thread.sleep(
2000
);
}
catch
(InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Thread t2 =
new
Thread() {
public
void
run() {
try
{
log(
"线程启动"
);
log(
"试图占有对象：lock"
);
lock.lock();
log(
"占有对象：lock"
);
log(
"进行5秒的业务操作"
);
Thread.sleep(
5000
);
}
catch
(InterruptedException e) {
e.printStackTrace();
}
finally
{
log(
"释放对象：lock"
);
lock.unlock();
}
log(
"线程结束"
);
}
};
t2.setName(
"t2"
);
t2.start();
}
}
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