Java ReentrantLock的可重入性与公平锁机制详解

ReentrantLock lock = new ReentrantLock();
public void func1() {
    lock.lock();
    try {
        inner();
    } finally {
        lock.unlock();
    }
}
public void func2() {
    lock.lock();  // 同一个线程可以再次获取锁
    try {
        // 操作
    } finally {
        lock.unlock();
    }
}

// 非公平锁
ReentrantLock unfairLock = new ReentrantLock();
// 公平锁
ReentrantLock fairLock = new ReentrantLock(true);

public void method() throws InterruptedException {
    lock.lockInterruptibly();  // 可中断的获取锁
    try {
        // 操作
    } finally {
        lock.unlock();
    }
}

public class Counter {
    private final ReentrantLock lock = new ReentrantLock();
    private int count = 0;
    public void increment() {
        lock.lock();  // 获取锁
        try {
            count++;
        } finally {
            lock.unlock();  // 必须放在finally中确保释放
        }
    }
}

lock.lock();
try {
    // 临界区代码
} finally {
    lock.unlock();
}

//嵌套层次过深
public void methodA() {
    lock.lock();
    try {
        methodB();
    } finally {
        lock.unlock();
    }
}
public void methodB() {
    lock.lock();  // 再次获取
    try {
        // ...
    } finally {
        lock.unlock();
    }
}