public interface Lock {
/**
* Acquires the lock.
*/
void lock();
/**
* Acquires the lock unless the current thread is
* {@linkplain Thread#interrupt interrupted}.
*/
void lockInterruptibly() throws InterruptedException;
/**
* Acquires the lock only if it is free at the time of invocation.
*/
boolean tryLock();
/**
* Acquires the lock if it is free within the given waiting time and the
* current thread has not been {@linkplain Thread#interrupt interrupted}.
*/
boolean tryLock(long time, TimeUnit unit) throws InterruptedException;
/**
* Releases the lock.
*/
void unlock();
}
package com.brickworkers;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class LockTest {
private Lock lock = new ReentrantLock();
//需要参与同步的方法
private void method(Thread thread){
lock.lock();
try {
System.out.println("线程名" thread.getName() "获得了锁");
}catch(Exception e){
e.printStackTrace();
} finally {
System.out.println("线程名" thread.getName() "释放了锁");
lock.unlock();
}
}
public static void main(String[] args) {
LockTest lockTest = new LockTest();
//线程1
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
lockTest.method(Thread.currentThread());
}
}, "t1");
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
lockTest.method(Thread.currentThread());
}
}, "t2");
t1.start();
t2.start();
}
}
//执行情况：线程名t1获得了锁
// 线程名t1释放了锁
// 线程名t2获得了锁
// 线程名t2释放了锁
package com.brickworkers;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class LockTest {
private Lock lock = new ReentrantLock();
//需要参与同步的方法
private void method(Thread thread){
/* lock.lock();
try {
System.out.println("线程名" thread.getName() "获得了锁");
}catch(Exception e){
e.printStackTrace();
} finally {
System.out.println("线程名" thread.getName() "释放了锁");
lock.unlock();
}*/
if(lock.tryLock()){
try {
System.out.println("线程名" thread.getName() "获得了锁");
}catch(Exception e){
e.printStackTrace();
} finally {
System.out.println("线程名" thread.getName() "释放了锁");
lock.unlock();
}
}else{
System.out.println("我是" Thread.currentThread().getName() "有人占着锁，我就不要啦");
}
}
public static void main(String[] args) {
LockTest lockTest = new LockTest();
//线程1
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
lockTest.method(Thread.currentThread());
}
}, "t1");
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
lockTest.method(Thread.currentThread());
}
}, "t2");
t1.start();
t2.start();
}
}
//执行结果： 线程名t2获得了锁
// 我是t1有人占着锁，我就不要啦
// 线程名t2释放了锁
/**
* Sync object for non-fair locks
*/
static final class NonfairSync extends Sync {
private static final long serialVersionUID = 7316153563782823691L;
/**
* Performs lock. Try immediate barge, backing up to normal
* acquire on failure.
*/
final void lock() {
if (compareAndSetState(0, 1))
setExclusiveOwnerThread(Thread.currentThread());
else
acquire(1);
}
protected final boolean tryAcquire(int acquires) {
return nonfairTryAcquire(acquires);
}
}
/**
* Sync object for fair locks
*/
static final class FairSync extends Sync {
private static final long serialVersionUID = -3000897897090466540L;
final void lock() {
acquire(1);
}
/**
* Fair version of tryAcquire. Don't grant access unless
* recursive call or no waiters or is first.
*/
protected final boolean tryAcquire(int acquires) {
final Thread current = Thread.currentThread();
int c = getState();
if (c == 0) {
if (!hasQueuedPredecessors() &&
compareAndSetState(0, acquires)) {
setExclusiveOwnerThread(current);
return true;
}
}
else if (current == getExclusiveOwnerThread()) {
int nextc = c acquires;
if (nextc < 0)
throw new Error("Maximum lock count exceeded");
setState(nextc);
return true;
}
return false;
}
}
public ReentrantLock() {
sync = new NonfairSync();//默认非公平锁
}
String str1="qwe"; String str2="asd"; String str3=str1 str2;
StringBuffer sb = new StringBuffer();
sb.append("qwe");
sb.append("asd");