Java 多线程编程

多线程编程是Java的重要特性之一，能够实现程序的并发执行。

线程基础

创建线程

// 方式1：继承Thread类
class MyThread extends Thread {
    @Override
    public void run() {
        System.out.println("线程正在运行");
    }
}

// 方式2：实现Runnable接口
class MyRunnable implements Runnable {
    @Override
    public void run() {
        System.out.println("线程正在运行");
    }
}

// 使用示例
MyThread thread1 = new MyThread();
thread1.start();

Thread thread2 = new Thread(new MyRunnable());
thread2.start();

// 方式3：使用Lambda表达式
Thread thread3 = new Thread(() -> {
    System.out.println("线程正在运行");
});
thread3.start();

线程生命周期

• NEW：新创建的线程
• RUNNABLE：可运行状态
• BLOCKED：阻塞状态
• WAITING：等待状态
• TIMED_WAITING：超时等待状态
• TERMINATED：终止状态

线程控制

// 线程休眠
Thread.sleep(1000); // 休眠1秒

// 线程加入
Thread thread = new Thread(() -> {
    // 执行任务
});
thread.start();
thread.join(); // 等待线程结束

// 线程中断
thread.interrupt();
boolean interrupted = Thread.interrupted();

线程同步

synchronized关键字

public class Counter {
    private int count = 0;
    
    // 同步方法
    public synchronized void increment() {
        count++;
    }
    
    // 同步代码块
    public void decrement() {
        synchronized (this) {
            count--;
        }
    }
}

Lock接口

public class Counter {
    private int count = 0;
    private final Lock lock = new ReentrantLock();
    
    public void increment() {
        lock.lock();
        try {
            count++;
        } finally {
            lock.unlock();
        }
    }
}

线程通信

wait/notify机制

public class Producer {
    private final Queue<String> queue;
    private final int capacity;

    public void produce(String data) throws InterruptedException {
        synchronized (queue) {
            while (queue.size() == capacity) {
                queue.wait();
            }
            queue.add(data);
            queue.notify();
        }
    }
}

public class Consumer {
    private final Queue<String> queue;

    public String consume() throws InterruptedException {
        synchronized (queue) {
            while (queue.isEmpty()) {
                queue.wait();
            }
            String data = queue.remove();
            queue.notify