试想一个情景，有两个线程同时工作，还有主线程，一个线程负责初始化网络，一个线程负责初始化资源，然后需要两个线程都执行完毕后，才能执行主线程

　　首先创建一个初始化资源的线程

　　

public class DataSourcesLoader implements Runnable {    /**     * Main method of the class     */    @Override    public void run() {                // Writes a messsage        System.out.printf("Begining data sources loading: %s\n",new Date());        // Sleeps four seconds        try {            TimeUnit.SECONDS.sleep(4);        } catch (InterruptedException e) {            e.printStackTrace();        }        // Writes a message        System.out.printf("Data sources loading has finished: %s\n",new Date());    }}

　　

　　然后创建一个初始化网络的线程

　　

public class NetworkConnectionsLoader implements Runnable {    /**     * Main method of the class     */    @Override    public void run() {        // Writes a message        System.out.printf("Begining network connections loading: %s\n",new Date());        // Sleep six seconds        try {            TimeUnit.SECONDS.sleep(6);        } catch (InterruptedException e) {            e.printStackTrace();        }        // Writes a message        System.out.printf("Network connections loading has finished: %s\n",new Date());    }}

　　

　　通过TimeUnit.SECONDS.sleep()方法; 进行休眠，

 

　　然后主线程执行，通过join方法，当一个线程对象的join方法被调用时，调用他的线程将会被挂起，知道这个线程来完成这些初始化任务，我们在主线程分别调用两个Thread的join方法，那么主线程会等到两个线程都执行完毕才会执行下去。

　　

public class Main {    /**     * Main method of the class. Create and star two initialization tasks     * and wait for their finish     * @param args     */    public static void main(String[] args) {        // Creates and starts a DataSourceLoader runnable object        DataSourcesLoader dsLoader = new DataSourcesLoader();        Thread thread1 = new Thread(dsLoader,"DataSourceThread");        thread1.start();        // Creates and starts a NetworkConnectionsLoader runnable object        NetworkConnectionsLoader ncLoader = new NetworkConnectionsLoader();        Thread thread2 = new Thread(ncLoader,"NetworkConnectionLoader");        thread2.start();        // Wait for the finalization of the two threads        try {            thread1.join();            thread2.join();        } catch (InterruptedException e) {            e.printStackTrace();        }        // Waits a message        System.out.printf("Main: Configuration has been loaded: %s\n",new Date());    }}