Java--线程

线程

继承Thread类

public class TestThread1 {public static void main(String args[]){Thread t = new MyThread(100);t.start();}}class MyThread extends Thread {private int n;;public MyThread( int n ){super();this.n=n;}public void run() {for(int i=0;i<n;i++) {System.out.print (" " + i);}}}

向Thread构造方法传递Runnable对象

public class TestThread2 {public static void main(String args[]) {MyTask mytask = new MyTask(10);Thread thread = new Thread(mytask);thread.start();//thread.setDaemon(true);for(int i=0; i<6; i++) {System.out.println("Main--" + i);try{Thread.sleep(500);}catch( InterruptedException e ){}}}}class MyTask implements Runnable {private int n;public MyTask(int n){this.n = n;}public void run() {for(int i=0; i<n; i++) {System.out.println(" " + i);try{Thread.sleep(500);}catch( InterruptedException e ){}}}}

public class TestThread4Anonymous {public static void main(String args[]) {new Thread(){public void run() {for(int i=0; i<10; i++)System.out.println(i);}}.start();new Thread( ( ) -> { for(int i=0; i<10; i++) System.out.println(" "+ i); } ).start();}}

多线程程序示例

import java.util.*;import java.text.*;public class TestThread3 {public static void main(String args[]) {Counter c1 = new Counter(1);Thread t1 = new Thread(c1);Thread t2 = new Thread(c1);Thread t3 = new Thread(c1);Counter c2 = new Counter(2);Thread t4 = new Thread(c2);Thread t5 = new Thread(c2);Thread t6 = new Thread(c2);TimeDisplay timer = new TimeDisplay();Thread t7 = new Thread(timer);t1.start();t2.start();t3.start();t4.start();t5.start();t6.start();t7.start();}}class Counter implements Runnable {int id;Counter(int id){this.id = id;}public void run() {int i=0;while( i++<=10 ){System.out.println("ID: " + id + "  No. " + i);try{ Thread.sleep(10); } catch( InterruptedException e ){}}}}class TimeDisplay implements Runnable {public void run(){int i=0;while( i++<=3 ){System.out.println( new SimpleDateFormat().format( new Date()));try{ Thread.sleep(40); } catch( InterruptedException e ){}}}}

同时运行的线程需要共享数据，有时会造成混乱。所以必须考虑线程的同步问题。
synchronized用来表示不允许其它线程中途插入。

wait()是让线程暂停运行，进入等待；notify()让线程继续运行

但是多线程可能造成线程的死锁。即线程一直处于等待状态。