java 多线程基础之一:多线程创建，执行，状态管理

By：Roy.LiuLast updated：2013-01-17

这几天在看一本书: 因为是纯英文版，平时也很少有时间专门去看，快到年底了，没心情做事，所以看看，顺便复习下多线程编程所以，就记录下来。

创建和运行一个线程 有两种方法创建一个线程:
1. 继承 Thread 类重载 Override run() 方法
2. 创建一个类实现 Runnable 接口，然后创建一个Thread类，用实现Runnable 接口的类的实例作为参数.

一个实例如下：

public class Calculator implements Runnable {
    private int number;
    public Calculator(int number) {
        this.number=number;
    }   
 
    public void run(){
        for (int i=1; i<=10; i++){
            System.out.printf("%s: %d * %d = %d\n",Thread.currentThread().getName(),number,i,i*number);
        }
    }
     
    public static void main(String[] args) {
        for (int i=1; i<=10; i++){
            Calculator calculator=new Calculator(i);
            Thread thread=new Thread(calculator);
            thread.start();
        }
    }
}

线程的启动必须用start() 方法，而不是run(),如果调用run()方法，跟普通方法没什么差别，只有用start()方法才能启动线程.

结果类似如下：

Thread-3: 4 * 10 = 40
Thread-7: 8 * 4 = 32
Thread-7: 8 * 5 = 40
Thread-7: 8 * 6 = 48
Thread-7: 8 * 7 = 56
Thread-7: 8 * 8 = 64
Thread-7: 8 * 9 = 72
Thread-7: 8 * 10 = 80
Thread-0: 1 * 7 = 7
Thread-0: 1 * 8 = 8
Thread-0: 1 * 9 = 9
Thread-0: 1 * 10 = 10

得到线程的相关信息，设置线程的相关信息
线程中的一些属性能够帮助我们确定是哪一个线程，知道线程的状态，以及优先级等，常用的属性如下：
ID: 每一个线程都有一个独立的ID，不会重复。
Name: 线程的名字
Priority:线程的优先级,优先级只能在 1 到 10 之间，其他都是非法的。10 是最高的优先级，1是最低的。一般情况下不需要设置线程的优先级，也许在有的情况下可以用到。
Status:线程的状态,有如下几种状态:new,runnable,blocked,waiting,time waiting,terminated

import java.lang.Thread.State;
 
public class Calculator implements Runnable {
    private int number;
 
    public Calculator(int number) {
        this.number=number;
    }   
 
    public void run() {
        for (int i=1; i<=10; i++){
            System.out.printf("%s: %d * %d = %d\n",Thread.currentThread().getName(),number,i,i*number);
        }
    }
     
    public static void main(String[] args) {
        System.out.printf("Minimum Priority: %s\n",Thread.MIN_PRIORITY);
        System.out.printf("Normal Priority: %s\n",Thread.NORM_PRIORITY);
        System.out.printf("Maximun Priority: %s\n",Thread.MAX_PRIORITY);
         
        Thread threads[];
        Thread.State status[];
         
        //发起10个线程，5个最高优先级，5个最低优先级,并设定线程的名字
        threads=new Thread[10];
        status=new Thread.State[10];
        for (int i=0; i<10; i++){
            threads[i]=new Thread(new Calculator(i));
            if ((i%2)==0){
                threads[i].setPriority(Thread.MAX_PRIORITY);
            } else {
                threads[i].setPriority(Thread.MIN_PRIORITY);
            }
            threads[i].setName("Thread "+i+"线程");
        }
         
         
        // Wait for the finalization of the threads. Meanwhile, 
        // write the status of those threads in a file
         
        try {
             
            for (int i=0; i<10; i++){
                System.out.println("Main : Status of Thread "+i+" : "+threads[i].getState());
                status[i]=threads[i].getState();
            }
 
            for (int i=0; i<10; i++){
                threads[i].start();
            }
             
            boolean finish=false;
            while (!finish) {
                for (int i=0; i<10; i++){
                    if (threads[i].getState()!=status[i]) {
                        writeThreadInfo(threads[i],status[i]);
                        status[i]=threads[i].getState();
                    }
                }
                 
                finish=true;
                for (int i=0; i<10; i++){
                    finish=finish &&(threads[i].getState()==State.TERMINATED);
                }
            }
             
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    /**
     *  打印线程状态
     * @param thread : Thread 
     * @param state : Old state of the thread
     */
    private static void writeThreadInfo(Thread thread, State state) {
        System.out.printf("Main : Id %d - %s\n",thread.getId(),thread.getName());
        System.out.printf("Main : Priority: %d\n",thread.getPriority());
        System.out.printf("Main : Old State: %s\n",state);
        System.out.printf("Main : New State: %s\n",thread.getState());
        System.out.println("Main : ************************************\n");
    }
}

这样就能设置线程的属性，以及的倒线程的属性. 可以看到结果如下:

Main : Old State: BLOCKED
Main : New State: BLOCKED
Main : ************************************
 
Thread 5线程: 5 * 9 = 45
Thread 5线程: 5 * 10 = 50
Main : Id 13 - Thread 5线程
Main : Priority: 1
Main : Old State: BLOCKED
Main : New State: TERMINATED
Main : ************************************

下一篇将继续讲线程的中断处理，以及异常处理.

From：一号门

Tags: java thread

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