java 多线程基础之一:多线程创建，执行，状态管理
这几天在看一本书:
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.
