Java中的ReentrantLock使用解析

static Lock lock = new ReentrantLock();
//修改时需要锁定的资源
static String text = "hello";

public static void modifyWithoutLock(){
    text += " "+Thread.currentThread().getName();
}

public static void main(String[] args) throws InterruptedException {
    modifyWithoutLock();
    for (int i=0;i<100;i++) {
        new Thread(() -> {
            modifyWithoutLock();
        }).start();
    }
    Thread.sleep(50);
    System.err.println(text.length());
}

public static void modify(){
	//使用lock方法枷锁
    lock.lock();
    try {
        text += " "+Thread.currentThread().getName();
    }catch (Exception e){
        e.printStackTrace();
    }
    finally {
    	//使用unlock方法解锁
        lock.unlock();
    }
}

public ReentrantLock() {
    sync = new NonfairSync();
}

/**
 * Creates an instance of {@code ReentrantLock} with the
 * given fairness policy.
 * 如果fair为true则构造是一个公平锁
 * @param fair {@code true} if this lock should use a fair ordering policy
 */
public ReentrantLock(boolean fair) {
    sync = fair ? new FairSync() : new NonfairSync();
}

private final Sync sync;

public void lock() {
    sync.lock();
}

public void unlock() {
    sync.release(1);
}