目录
4.线程状态，线程可以处于以下状态之一：(Thread.State)
1.线程休眠：（sleep）
sleep（时间）指定当前线程阻塞的毫秒数；
sleep 存在异常InterruptedException；
sleep 时间达到后线程进入就绪状态
sleep 可以模拟网络延时，倒计时等。
每一个对象都有一个锁，sleep不会释放锁；
/*模拟网络延迟：放大问题的发生性*/
public class TestSleep implements Runnable {
//票数
private int ticketNums = 10;
@Override
public void run() {
while (true) {
if (ticketNums <= 0) {
break;
}
//模拟延时
try {
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "--->拿到了第" + ticketNums-- + "票");
}
}
public static void main(String[] args) {
TestSleep testSleep = new TestSleep();
new Thread(testSleep,"小明").start();
new Thread(testSleep,"小红").start();
new Thread(testSleep,"小黄牛").start();
}
}
///模拟倒计时
import java.text.SimpleDateFormat;
import java.util.Date;
public class TestSleep2 {
public static void testDown() throws InterruptedException {
int num = 10;
while (true) {
Thread.sleep(1000);
System.out.println(num--);
if (num == 0) {
break;
}
}
}
/**
* 打印当前时间
*/
public static void printNowDate() {
//打印当前系统时间
Date stattTime = new Date(System.currentTimeMillis());
while (true) {
try {
//休眠1秒
Thread.sleep(1000);
System.out.println(new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss").format(stattTime)); //格式化时间,并输出时间
stattTime = new Date(System.currentTimeMillis()); //更新获取时间
} catch (Exception e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
printNowDate();
}
}
2.线程礼让：（yield）
1.礼让线程，让当前正在执行的线程暂停，但不阻塞
2.将线程从运行状态转为就绪状态
3.让cpu 重新调度，礼让不一定成功！看cpu
public class TestYield {
public static void main(String[] args) {
MyYield myYield = new MyYield();
new Thread(myYield,"A").start();
new Thread(myYield,"B").start();
}
}
class MyYield implements Runnable {
@Override
public void run() {
System.out.println(Thread.currentThread().getName()+"线程开始执行");
Thread.yield();//礼让
System.out.println(Thread.currentThread().getName()+"线程停止执行");
}
}
3.线程强行停止：（join）
Join 合并线程，待此线程执行完成后，再执行其他线程（想象为插队）
public class TestJoin implements Runnable {
@Override
public void run() {
for (int i = 0; i < 100; i++) {
System.out.println("线程VIP 来了" + i);
}
}
public static void main(String[] args) throws InterruptedException {
TestJoin testJoin = new TestJoin();
Thread thread = new Thread(testJoin);
//启动线程
thread.start();
//主线程
for (int i = 0; i < 200; i++) {
if (i == 100) {
thread.join();//插队
}
System.out.println("main" + i);
}
}
}
4.线程状态，线程可以处于以下状态之一：(Thread.State)
NEW
尚未启动的线程处于此状态
RUNNABLE
在Java虚拟机中执行的线程处于此状态
BLOCKED
被阻塞等待监视器锁定的线程处于此状态
WAITING
正在等待另一个线程执行特定动作的线程处于此状态
TIMED WAITING
正在等待另一个线程执行动作达到指定等待时间的线程处于此状态
TERMINATED
已退出的线程处于此状态
5.线程优先级：
设置线程优先级：setPriority（1---10） 优先级高的获取cpu的概率大，不一定高的就先跑
获取线程优先级：getPriority（）
6.守护线程：
thread.setDaemon(true); //默认为false表示用户线程，正常线程都是用户线程
You线程执行完，God守护线程也会停止
package 多线程;
public class ThreadDaemon {
public static void main(String[] args) {
God god = new God();
You you = new You();
Thread thread=new Thread(god);
thread.setDaemon(true); //默认为false表示用户线程，正常线程都是用户线程
thread.start();
new Thread(you).start(); //用户线程
}
}
class God implements Runnable{
@Override
public void run() {
while (true){
System.out.println("你好呀");
}
}
}
class You implements Runnable{
@Override
public void run() {
for (int i = 0; i < 100; i++) {
System.out.println("你活了"+i);
}
System.out.println("没了");
}
}
7.线程同步：
三大不安全案例 （sleep）方法问题的发生性
package 多线程.syn;
/**
* 模拟买票
* 线程不安全
* 可能会出现-1
*
*/
public class UnsafeBuyTicket {
public static void main(String[] args) {
Buy buy = new Buy();
Thread thread1=new Thread(buy,"小红");
Thread thread2=new Thread(buy,"小明");
Thread thread3=new Thread(buy,"小刚");
thread1.start();
thread2.start();
thread3.start();
}
}
class Buy implements Runnable{
private int ticketNums=10;
boolean flag=true;
@Override
public void run() {
while (flag) {
if(ticketNums<=0){
flag=false;
return;
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"第几章"+ticketNums--);
}
}
}package 多线程.syn;
/**
* 模拟银行取钱
* 大于100都进去取钱
* 导致超出取钱
*/
public class UnsafeBank {
public static void main(String[] args) {
Account account=new Account(100,"小明");
Drawing you=new Drawing(account,50,"你");
Drawing me=new Drawing(account,100,"我");
you.start();
me.start();
}
}
//账户
class Account{
int money;
String name;
public Account(int money, String name) {
this.money = money;
this.name = name;
}
}
//银行
class Drawing extends Thread{
Account account; //账户
int drawingMoney; //取了多少钱
int nowMoney; //现在手里有多少
public Drawing(Account account, int drawingMoney, String name) {
super(name); //super必须在第一个
this.account = account;
this.drawingMoney = drawingMoney;
}
//取钱
@Override
public void run() {
//判断有没有钱
if (account.money-drawingMoney<0){
System.out.println(this.getName()+"钱不够");
return;
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money=account.money-drawingMoney; //账户的钱
nowMoney=nowMoney+drawingMoney; //手里的钱
System.out.println(account.name+"余额为："+account.money);
//Thread.currentThread().getName()==this.getName
System.out.println(this.getName()+"手里的钱:"+nowMoney);
}
}package 多线程.syn;
/**
*用10000个线程打印10000个数据，导致数据少
*问题：两个线程同时操作一个位置，会覆盖不会增加
*/
import java.util.ArrayList;
import java.util.List;
public class UnsafeList {
public static void main(String[] args) throws InterruptedException {
List<String> list = new ArrayList<>();
for (int i = 0; i < 10000; i++) {
new Thread(()->{
list.add(Thread.currentThread().getName());
}).start();
}
Thread.sleep(2000);
System.out.println(list.size());
}
}同步方法：（会影响效率）锁的是this
在方法前加 ：synchronized 排队
@Override
public void run() {
while (flag) {
mai();
}
}
private synchronized void mai(){
if(ticketNums<=0){
flag=false;
return;
}
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+"第几章"+ticketNums--);
}
锁的对象是变化的量，需要增删改查的，默认为this，
//取钱
@Override
public void run() {
synchronized(account){
//判断有没有钱
if (account.money-drawingMoney<0){
System.out.println(this.getName()+"钱不够");
return;
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money=account.money-drawingMoney; //账户的钱
nowMoney=nowMoney+drawingMoney; //手里的钱
System.out.println(account.name+"余额为："+account.money);
//Thread.currentThread().getName()==this.getName
System.out.println(this.getName()+"手里的钱:"+nowMoney);
}
不加sleep线程会提前跑完，还是不安全 public class UnsafeList { public static void main(String[] args) throws InterruptedException { List<String> list = new ArrayList<>(); for (int i = 0; i < 10000; i++) { new Thread(()->{ synchronized (list){ list.add(Thread.currentThread().getName()); } }).start(); } Thread.sleep(2000); System.out.println(list.size()); } }
8.死锁（多个线程互相抱着对方的资源，然后停止）
public class TestLock {
public static void main(String[] args) {
Makeup g1 = new Makeup(0,"灰姑凉");
Makeup g2 = new Makeup(1,"白雪公主");
g1.start();
g2.start();
}
}
class Lipstick {} //口红
class Mirror {} //镜子
class Makeup extends Thread {
//需要的资源只有一份，用static 来保证只有一份
static Lipstick lipstick = new Lipstick();
static Mirror mirror = new Mirror();
int choice;//选择
String girlName;//使用化妆品的人
public Makeup(int choice, String girlName) {
this.choice = choice;
this.girlName = girlName;
}
@Override
public void run() {
try {
makeup();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//化妆，互相持有对方的锁，就是需要拿到对方的资源
private void makeup() throws InterruptedException {
if (choice == 0) {
synchronized (lipstick) {//获得口红的锁
System.out.println(this.girlName + "获得口红的锁");
Thread.sleep(100);
synchronized (mirror) {//一秒钟后想获得镜子
System.out.println(this.girlName + "获得镜子的锁");
}
}
} else {
synchronized (mirror) {//想获得镜子的锁
System.out.println(this.girlName + "获得镜子的锁");
Thread.sleep(100);
synchronized (lipstick) {//一秒钟后想获得口红
System.out.println(this.girlName + "获得口红的锁");
}
}
}
}
}
产生死锁的四个必要条件：
1.互斥条件：一个资源每次只能被一个进程使用。
2.请求与保持条件：一个进程因请求资源而阻塞，对已获得的资源保持不放。
3.不剥夺条件：进程已获得的资源，在未使用完之前，不能强行剥夺。
4.循环等待条件：若干个进程之间形成一种头尾相接的循环等待资源关系。
9.Lock:(ReentrantLock)
手动开关
import java.util.concurrent.locks.ReentrantLock;
public class TestLock {
public static void main(String[] args) {
TestLock2 lock2 = new TestLock2();
new Thread(lock2,"1").start();
new Thread(lock2,"2").start();
new Thread(lock2,"3").start();
}
}
class TestLock2 implements Runnable{
int ticketNums = 10;
//定义lock锁
private final ReentrantLock lock = new ReentrantLock();
@Override
public void run() {
while (true){
try {
lock.lock();//加锁
if (ticketNums >0){
try {
Thread.sleep(100);
}catch (Exception e){
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+" "+ticketNums--);
}else {
break;
}
}catch (Exception e){
e.printStackTrace();
}finally {
lock.unlock();//解锁
}
}
}
}
10.生产者消费者：
public class TestPC {
public static void main(String[] args) {
SynContainer container = new SynContainer();
new Productor(container).start();
new Consumer(container).start();
}
}
//生产者
class Productor extends Thread {
SynContainer container;
public Productor(SynContainer container) {
this.container = container;
}
//生产
@Override
public void run() {
for (int i = 1; i <= 20; i++) {
container.push(new Chiken(i));
System.out.println("生产了"+i+"只鸡");
}
}
}
//消费者
class Consumer extends Thread {
SynContainer container;
public Consumer(SynContainer container) {
this.container = container;
}
//生产
@Override
public void run() {
for (int i = 1; i <= 20; i++) {
Chiken pop = container.pop();
System.out.println("消费了第"+pop.id+"只鸡");
}
}
}
//产品
class Chiken {
int id;//编号
public Chiken(int id) {
this.id = id;
}
}
//缓冲区
class SynContainer {
//需要一个容器大小
Chiken[] chikens = new Chiken[10];
//容器计数器
int count = 0;
//生产者放入产品
public synchronized void push(Chiken chiken) {
//如果容器满了，就需要等待消费者消费
if (count == chikens.length) {
//通知消费者消费，生产者等待
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果容器没有满，我们就需要丢入产品
chikens[count] = chiken;
count++;
//通知消费者消费
this.notifyAll(); //唤醒
}
//通知消费者消费
public synchronized Chiken pop() {
//判断能否消费
if (count == 0) {
//等待生产者生产，消费者等待
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果可以消费
count--;
Chiken chiken = chikens[count];
//吃完了，通知生产者生产
this.notifyAll();
return chiken;
}
}