编写两个线程类，分别命名为First和Second，可选用继承Thread类或者执行Runnable接口的方法创建这两个线程类，线程可循环3次输出自己线程的名字；

好的，以下是使用继承Thread类的方法创建两个线程类First和Second：

public class First extends Thread {
    public void run() {
        for (int i = 1; i <= 3; i++) {
            System.out.println("Thread name: " + Thread.currentThread().getName());
        }
    }
}

public class Second extends Thread {
    public void run() {
        for (int i = 1; i <= 3; i++) {
            System.out.println("Thread name: " + Thread.currentThread().getName());
        }
    }
}

以下是使用执行Runnable接口的方法创建两个线程类First和Second：

public class First implements Runnable {
    public void run() {
        for (int i = 1; i <= 3; i++) {
            System.out.println("Thread name: " + Thread.currentThread().getName());
        }
    }
}

public class Second implements Runnable {
    public void run() {
        for (int i = 1; i <= 3; i++) {
            System.out.println("Thread name: " + Thread.currentThread().getName());
        }
    }
}

在主函数中，我们可以创建两个线程对象并调用start()方法启动线程：

public static void main(String[] args) {
    Thread t1 = new First();
    Thread t2 = new Second();

    t1.start();
    t2.start();
}

运行程序后，会输出以下结果：

Thread name: Thread-0
Thread name: Thread-0
Thread name: Thread-0
Thread name: Thread-1
Thread name: Thread-1
Thread name: Thread-1