java需要关注的知识点---并发之后台线程
所谓的后台线程，是指在程序运行的时候在后台提供一种通用服务的线程，并且这种线程并不属于程序中不可或缺的部分。因此，当所有的非后台线程结束的时候，程序也就终止，同时会杀死所有的后台线程。
package com.thread;import java.util.concurrent.TimeUnit;public class SimpleDaemons implements Runnable{public void run() {while(true) {try {TimeUnit.MILLISECONDS.sleep(100);System.out.println(Thread.currentThread() + " " + this);} catch (InterruptedException e) {e.printStackTrace();}}}public static void main(String[] args) throws InterruptedException {for (int i = 0; i < 10; i++) {Thread daemo = new Thread(new SimpleDaemons());daemo.setDaemon(true);daemo.start();}System.out.println("All daemons started");//如果去掉sleep，run方法中的语句不会输出。说明main也是非后台线程TimeUnit.MILLISECONDS.sleep(180);}}package com.thread;import java.io.IOException;public class ResponsveUI extends Thread {private static volatile double d = 1;public ResponsveUI() {setDaemon(true);start();}public void run() {while(true) {d = d + (Math.PI + Math.E);}}public static void main(String[] args) throws Exception {//new UnresponsiveUI(); //must kill this processnew ResponsveUI();System.in.read();System.out.println(d);}}class UnresponsiveUI {private volatile double d = 1;public UnresponsiveUI() throws Exception{while (d > 0) {d = d + (Math.PI + Math.E);}System.in.read();}}