Java多线程03_线程状态、优先级、用户线程和守护线程
线程方法:
setPriority() 更改线程优先级
static void sleep() 线程休眠
void join() 插队
static void yield() 礼让
void interrupt() 中断线程
boolean isAlive() 是否存活
停止线程:
不推荐JDK提供的stop()、destory()方法 【已废弃】
推荐让线程正常停止,不要死循环!
建议使用一个标志位进行终止,当flag=false,则终止线程运行
public class TestStop implements Runnable{
private boolean flag = true;
@Override
public void run() {
int i = 0;
while(flag) {
System.out.println("run...Thread"+i++);
}
}
//设置公开方法利用标志位停止线程
public void stopThread() {
this.flag = false;
System.out.println("线程停止了");
}
public static void main(String[] args) {
TestStop testStop = new TestStop();
new Thread(testStop).start();
for(int i=0;i<1000;i++) {
System.out.println("main...,"+i);
if(i==900) {
testStop.stopThread();
}
}
}
}
线程休眠:
sleep方法存在异常:InterruptedException
sleep时间结束,线程进入就绪状态
每个对象都有一个锁,sleep不会释放锁
Thread.sleep(1000);
线程礼让:
让当前执行的线程暂停,但不阻塞
将线程从运行状态转为就绪状态
礼让不一定成功,看cpu心情
Thread.yield();
Join合并线程,待此线程执行完成后,再执行其他线程,其他线程阻塞(插队)
main线程和Thread线程交替执行,当main线程执行到200时,Thread线程插队,一直到执行结束,main线程才能重新执行
package com.blu.demo1;
public class TestJoin implements Runnable{
@Override
public void run() {
for(int i = 0;i < 1000;i++) {
System.out.println("vip线程正在执行....."+i);
}
}
public static void main(String[] args) throws InterruptedException {
TestJoin testJoin = new TestJoin();
Thread thread = new Thread(testJoin);
thread.start();
for(int i = 0;i < 1000;i++) {
if(i==200) {
thread.join();
}
System.out.println("main线程正在执行....."+i);
}
}
}
getState()监测线程状态:
返回枚举类型:
NEW
RUNNABLE
BLOCKED
WAITING
TIMED_WAITING
TERMINATED
线程优先级:
线程优先级用1-10之间的整数表示,1为最低优先级,10为最高优先级
主线程优先级默认为5,且不可修改
枚举
Thread.MAX_PRIORITY = 10
Thread.NORM_PRIORITY = 5
Thread.MIN_PRIORITY = 1
优先级高不一定先执行,由CPU调度决定
public class TestPriority {
public static void main(String[] args) {
//主线程优先级
System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
MyPriority myPriority = new MyPriority();
Thread t1 = new Thread(myPriority);
Thread t2 = new Thread(myPriority);
Thread t3 = new Thread(myPriority);
Thread t4 = new Thread(myPriority);
Thread t5 = new Thread(myPriority);
Thread t6 = new Thread(myPriority);
//设置优先级
t1.start();
t2.setPriority(1);
t3.setPriority(4);
t4.setPriority(Thread.MAX_PRIORITY);
t5.setPriority(5);
t6.setPriority(7);
t2.start();
t3.start();
t4.start();
t5.start();
t6.start();
}
}
class MyPriority implements Runnable{
@Override
public void run() {
System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
}
}
守护线程
线程分为用户线程(比如main) 和 守护线程(比如gc)
虚拟机必须确保用户线程执行完毕,不用等待守护线程执行完毕
当只剩下守护线程时,JVM就会退出,只要存在一个用户线程,JVM就不会退出
public class TestDaemon {
public static void main(String[] args) {
God god = new God();
You you = new You();
Thread thread = new Thread(god);
thread.setDaemon(true);
thread.start();
new Thread(you).start();
}
}
class God implements Runnable{
@Override
public void run() {
while(true) {
System.out.println("上帝保佑着你");
}
}
}
class You implements Runnable{
@Override
public void run() {
for(int i = 0;i<=100;i++) {
System.out.println("你开心地活了"+i+"年");
}
System.out.println("GoodBye,World!");
}
}