java中实现多线程有几种方式，请举例

Java中实现多线程的方式有以下几种：

1. 继承Thread类，重写run()方法。例如：

class MyThread extends Thread {
    public void run() {
        // 线程执行代码
    }
}
MyThread thread = new MyThread();
thread.start();

2. 实现Runnable接口，重写run()方法。例如：

class MyRunnable implements Runnable {
    public void run() {
        // 线程执行代码
    }
}
MyRunnable runnable = new MyRunnable();
Thread thread = new Thread(runnable);
thread.start();

3. 实现Callable接口，重写call()方法。例如：

class MyCallable implements Callable<String> {
    public String call() throws Exception {
        // 线程执行代码
        return result;
    }
}
MyCallable callable = new MyCallable();
ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(callable);

4. 使用线程池。例如：

ExecutorService executor = Executors.newFixedThreadPool(10);
for (int i = 0; i < 100; i++) {
    Runnable task = new MyRunnable();
    executor.submit(task);
}
executor.shutdown();