常见的实现多线程的方式：Thread和Runnable
其他方式：实现Callable接口通过Future/FutureTask包装器来创建Thread线程，通过线程池实现有返回结果的线程
- Runnable，Runnable是一个接口，仅包含了一个run()方法。
@FunctionalInterface
public interface Runnable {
/**
* When an object implementing interface <code>Runnable</code> is used
* to create a thread, starting the thread causes the object's
* <code>run</code> method to be called in that separately executing
* thread.
* <p>
* The general contract of the method <code>run</code> is that it may
* take any action whatsoever.
*
* @see java.lang.Thread#run()
*/
public abstract void run();
}
Runnable实例
public class MyThread2 implements Runnable {
private int ticket = 20;
@Override
public void run() {
for(int i=0;i<30;i++){
if(this.ticket>0){
System.out.println(Thread.currentThread().getName()+" 卖票：ticket"+this.ticket--);
}
}
}
public static void main(String[] args) {
MyThread2 myThread2 = new MyThread2();
//主线程main创建并启动3个子线程，而且这3个子线程都是基于“myThread2这个Runnable对象”而创建的。这3个子线程一共卖出了20张票。
//这3个子线程可能会由于并发问题，导致卖出多余20张票
Thread t1 = new Thread(myThread2);
Thread t2 = new Thread(myThread2);
Thread t3 = new Thread(myThread2);
t1.start();
t2.start();
t3.start();
}
}
运行结果
Thread-0 卖票：ticket20 ——并发
Thread-1 卖票：ticket20
Thread-2 卖票：ticket19
Thread-1 卖票：ticket17
Thread-0 卖票：ticket18
Thread-1 卖票：ticket15
Thread-2 卖票：ticket16
Thread-1 卖票：ticket13
Thread-1 卖票：ticket11
Thread-1 卖票：ticket10
Thread-1 卖票：ticket9
Thread-0 卖票：ticket14
Thread-1 卖票：ticket8
Thread-2 卖票：ticket12
Thread-1 卖票：ticket6
Thread-0 卖票：ticket7
Thread-1 卖票：ticket4
Thread-0 卖票：ticket3
Thread-0 卖票：ticket2
Thread-2 卖票：ticket5
Thread-1 卖票：ticket1
结果说明：
(01) 和下面“MyThread继承于Thread”不同；这里的MyThread实现了Runnable接口。
(02) 主线程main创建并启动3个子线程，而且这3个子线程都是基于“myThread2这个Runnable对象”而创建的。运行结果是这3个子线程一共卖出了20张票。这说明它们是共享了MyThread接口的。
(03) 因为并发的原因导致可能多余20张票。
Runnable实现了资源的共享。即，多个线程都是基于某一个Runnable对象建立的，它们会共享Runnable对象上的资源。
通常，建议通过“Runnable”实现多线程！
- Thread，Thread本身是实现了Runnable接口的类。
public class MyThread1 extends Thread{
private int ticket = 10;
public void run(){
for(int i=0; i<5; i++){
if(this.ticket > 0){
System.out.println(this.getName()+" 卖票：ticket"+this.ticket--);
}
}
}
public static void main(String[] args) {
//主线程main()创建了3个MyThread子线程，每个子线程都各自卖出5张票
MyThread1 t1 = new MyThread1();
MyThread1 t2 = new MyThread1();
MyThread1 t3 = new MyThread1();
t1.start();
t2.start();
t3.start();
}
}
运行结果
Thread-0 卖票：ticket10
Thread-1 卖票：ticket10
Thread-0 卖票：ticket9
Thread-1 卖票：ticket9
Thread-1 卖票：ticket8
Thread-1 卖票：ticket7
Thread-1 卖票：ticket6
Thread-0 卖票：ticket8
Thread-0 卖票：ticket7
Thread-0 卖票：ticket6
Thread-2 卖票：ticket10
Thread-2 卖票：ticket9
Thread-2 卖票：ticket8
Thread-2 卖票：ticket7
Thread-2 卖票：ticket6
结果说明：
(01) MyThread继承于Thread，它是自定义的线程。
(02) 主线程main创建并启动3个MyThread子线程。每个子线程都各自卖出了10张票。
