Java多线程
多线程
线程开启后不一定立即执行，由CPU调度
1. 多线程创建方式
1.1创建线程方式1：继承Thread类，重写run方法线程体，调用start();
/*
线程开启后不一定立即执行，由cpu安排调度
*/
//创建线程方式1：继承Thread类，重写run方法线程体，调用start();
//继承Thread类
public class TestThread1 extends Thread{
//重写run方法线程体
public void run() {
for (int i = 0; i < 20; i++) {
System.out.println("Jay " + i);
}
}
public static void main(String[] args) {
//创建一个线程对象
TestThread1 testThread1 = new TestThread1();
//调用start()方法开启线程
testThread1.start();
for (int i = 0; i < 20; i++) {
System.out.println("Soul " + i);
}
}
}
package Jay;
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;
/*
练习Thread，实现多线程同步下载图片
*/
public class TestThread2 extends Thread{
private String url;
private String name;
public TestThread2(String url, String name){
this.url = url;
this.name = name;
}
//下载图片的线程执行体
public void run(){
WebDownloader webDownloader = new WebDownloader();
webDownloader.downloader(url, name);
System.out.println(name + " 文件下载成功");
}
public static void main(String[] args) {
TestThread2 t1 = new TestThread2("https://cdn.jsdelivr.net/gh/filess/img17@main/2021/05/07/1620371242789-b286c6f7-a06c-48c7-a53b-3a86d18cea97.png", "p1.png");
TestThread2 t2 = new TestThread2("https://cdn.jsdelivr.net/gh/filess/img16@main/2021/05/07/1620377761880-1d4715d4-482c-4d52-a5aa-210a1a354c77.png", "p2.png");
TestThread2 t3 = new TestThread2("https://cdn.jsdelivr.net/gh/filess/img8@main/2021/05/07/1620377156603-8b53ee53-8de0-4f81-b667-3df6ce555064.png", "p3.png");
t1.start();
t2.start();
t3.start();
}
}
//下载器
class WebDownloader{
public void downloader(String url, String name){
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常，downloader下载出现问题");
}
}
}
1.2 创建线程方法2：实现runnable接口，重写run方法执行线程需要丢入runnable接口实现类，调用start方法
//创建线程方法2：实现runnable接口，重写run方法执行线程需要丢入runnable接口实现类，调用start方法
public class TestThread3 implements Runnable{
//重写run方法线程体
public void run() {
for (int i = 0; i < 20; i++) {
System.out.println("Jay " + i);
}
}
public static void main(String[] args) {
//创建runnable接口的实现类对象
TestThread3 testThread3 = new TestThread3();
//创建线程对象，通过线程对象来开启我的线程（代理）
new Thread(testThread3).start();
for (int i = 0; i < 20; i++) {
System.out.println("Soul " + i);
}
}
}
多个线程同时操作同一对象，线程不安全，数据紊乱
//多个线程同时操作同一对象，线程不安全，数据紊乱
//买火车票的例子
public class TestThread4 implements Runnable{
private int ticketNums = 10;
public void run(){
while (true){
if (ticketNums <= 0){
break;
}
/*try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}*/
System.out.println(Thread.currentThread().getName() + "-->拿到了第" + ticketNums-- + "票");
}
}
public static void main(String[] args) {
TestThread4 ticket = new TestThread4();
new Thread(ticket, "小明").start();
new Thread(ticket, "小红").start();
new Thread(ticket, "小黄").start();
}
}
龟兔赛跑
import kotlin.reflect.jvm.internal.impl.descriptors.Visibilities;
//模拟龟兔赛跑
public class Race implements Runnable{
private static String winner;
@Override
public void run() {
for (int i = 1; i <= 100; i++) {
if (Thread.currentThread().getName().equals("兔子") && i % 60 == 0)
{
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (gameOver(i)) break;
System.out.println(Thread.currentThread().getName() + "-->跑了" + i + "步");
}
}
//判断是否完成比赛
private boolean gameOver (int step){
if (winner != null){
return true;
}
if (step >= 100) {
winner = Thread.currentThread().getName();
System.out.println("Winner is " + winner);
return true;
}
return false;
}
public static void main(String[] args) {
Race race = new Race();
new Thread(race, "兔子").start();
new Thread(race, "乌龟").start();
}
}
1.3 线程创建方式3：实现callable接口
import org.apache.commons.io.FileUtils;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
//线程创建方式三：实现callable接口
/*
callable的好处
1、可以定义返回值
2、可以抛出异常
*/
public class TestCallable implements Callable<Boolean> {
private String url;
private String name;
public TestCallable(String url, String name){
this.url = url;
this.name = name;
}
//下载图片的线程执行体
public Boolean call(){
WebDownloader webDownloader = new WebDownloader();
webDownloader.downloader(url, name);
System.out.println(name + " 文件下载成功");
return true;
}
public static void main(String[] args) {
TestCallable t1 = new TestCallable("https://cdn.jsdelivr.net/gh/filess/img17@main/2021/05/07/1620371242789-b286c6f7-a06c-48c7-a53b-3a86d18cea97.png", "p1.png");
TestCallable t2 = new TestCallable("https://cdn.jsdelivr.net/gh/filess/img16@main/2021/05/07/1620377761880-1d4715d4-482c-4d52-a5aa-210a1a354c77.png", "p2.png");
TestCallable t3 = new TestCallable("https://cdn.jsdelivr.net/gh/filess/img8@main/2021/05/07/1620377156603-8b53ee53-8de0-4f81-b667-3df6ce555064.png", "p3.png");
//创建执行服务：
ExecutorService ser = Executors.newFixedThreadPool(3);
//提交执行
Future<Boolean> r1 = ser.submit(t1);
Future<Boolean> r2 = ser.submit(t2);
Future<Boolean> r3 = ser.submit(t3);
//关闭服务
ser.shutdownNow();
}
}
//下载器
class WebDownloader{
public void downloader(String url, String name){
try {
FileUtils.copyURLToFile(new URL(url), new File(name));
} catch (IOException e) {
e.printStackTrace();
System.out.println("IO异常，downloader下载出现问题");
}
}
}
2. 静态代理模式
package Jay;
/*
静态代理：
1、真实对象和代理对象都要实现一个接口
2、代理对象需要代理真是角色
*/
public class StaticProxy{
public static void main(String[] args) {
new MarryCompany(new you()).happyMarry();
}
}
interface Marry{
public void happyMarry();
}
//真实角色结婚
class you implements Marry{
@Override
public void happyMarry() {
System.out.println("源宝结婚了");
}
}
//婚庆公司代理
class MarryCompany implements Marry{
private Marry target;
public MarryCompany(Marry target) {
this.target = target;
}
@Override
public void happyMarry() {
berfore();
this.target.happyMarry();//这是真实对象
after();
}
private void after() {
System.out.println("收尾款");
}
private void berfore() {
System.out.println("布置场地");
}
}
3. Lamda表达式
3.1 为什么使用lamda表示
- 避免匿名内部类定义过多
- 使代码看起来简洁，去掉无意义的代码，只留下核心逻辑
- 其实质属于函数式编程的概念
3.2 函数式接口的定义
- 任何接口，如果只包含唯一一个抽象方法，那么它就是一个函数式接口
- 对于函数式接口，我们可以通过lamda表达式来创建接口的对象
package thread.lamda;
/*
推导lamda表达式
*/
public class TestLamda01 {
//3.静态内部类
static class Like2 implements ILike{
@Override
public void lamda() {
System.out.println("I like lamda2!");
}
}
public static void main(String[] args) {
ILike like = new Like();
like.lamda();
like = new Like2();
like.lamda();
//4.局部内部类
class Like3 implements ILike{
@Override
public void lamda() {
System.out.println("I like lamda3!");
}
}
like = new Like3();
like.lamda();
//5.匿名内部类，没有类的名称，必须借助接口或者父类
like = new ILike() {
@Override
public void lamda() {
System.out.println("I like lamda4!");
}
};
like.lamda();
//6.用lamda简化
like = ()->{
System.out.println("I like lamda5!");
};
like.lamda();
}
}
//1.定义一个函数式接口
interface ILike{
void lamda();
}
//2.实现类
class Like implements ILike{
@Override
public void lamda() {
System.out.println("I like lamda!");
}
}
package thread.lamda;
public class TestLamda02 {
//静态内部类
static class love2 implements ILove{
@Override
public void love(int a) {
System.out.println("I love" + a);
}
}
public static void main(String[] args) {
//普通类实现
ILove love = new love();
love.love(1);
//静态内部类实现
love = new love2();
love.love(2);
//局部内部类
class love3 implements ILove{
@Override
public void love(int a) {
System.out.println("I love" + a);
}
}
new love3().love(77);
//匿名内部类
love = new ILove() {
@Override
public void love(int a) {
System.out.println("I love" + a);
}
};
love.love(3);
//lamda 简化
love = (int a)->{
System.out.println("I love" + a);
};
love.love(4);
}
}
interface ILove{
void love(int a);
}
class love implements ILove{
@Override
public void love(int a) {
System.out.println("I love" + a);
}
}
3.3 lamda简化形式
//简化形式1
love = (a) -> {
System.out.println("I love" + a);
};
//简化形式2（参数<=1）
love = a -> {
System.out.println("I love" + a);
};
//简化形式3（代码只有一行）
love = a -> System.out.println("I love" + a);
4. 线程状态和方法
线程一旦进入死亡状态，就不能再次启动
4.1 五大状态
* 创建状态（new）
* 就绪状态（start）
* 运行状态
* 阻塞状态（sleep，wait）
* 死亡状态
4.2 线程方法
4.3 停止线程
- 推荐线程自己停下来（不建议死循环）
- 建议使用一个标志位进行终止变量（当flag= false，则终止线程运行）
- 不要使用stop或者destroy等过时或者JDK不建议使用的方法
package thread.methods;
//测试stop
public class TestStop implements Runnable{
//1.设置一个标志位
private boolean flag = true;
@Override
public void run() {
int i = 0;
while (flag){
System.out.println("run ....... Thread" + i++);
}
}
//2.设置一个公开的方法停止线程，转换标志位
public void stop(){
this.flag = false;
}
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.stop();
System.out.println("线程已经停止");
}
}
}
}
4.4 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
4.5 线程礼让（yield）
package thread.methods;
//测试礼让线程
public class TestYield {
public static void main(String[] args) {
//lamda表达式
Runnable myYield = ()->{
System.out.println(Thread.currentThread().getName() + "线程开始执行");
Thread.yield();
System.out.println(Thread.currentThread().getName() + "线程运行结束");
};
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();
// System.out.println(Thread.currentThread().getName() + "线程运行结束");
// }
//}
4.6 合并线程（Join）
* 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
* 可以想象成插队
package thread.methods;
//测试join方法
public class TestJoin implements Runnable {
@Override
public void run() {
for (int i = 0; i < 1000; i++) {
System.out.println("VIP来了" + i);
}
}
public static void main(String[] args) throws InterruptedException {
//启动我们的线程
TestJoin testJoin = new TestJoin();
Thread thread = new Thread(testJoin);
thread.start();
//主线程
for (int i = 0; i < 500; i++) {
if (i == 100){
thread.join();
}
System.out.println("main" + i);
}
}
}
4.7 观测线程状态
package thread.state;
public class TestState {
public static void main(String[] args) throws InterruptedException {
Thread thread = new Thread(()->{
for (int i = 0; i < 5; i++) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("/////");
});
//观察状态(new)
Thread.State state = thread.getState();
System.out.println(state);
//run
thread.start();
state = thread.getState();
System.out.println(state);
//只要线程不终止，就一直输出状态
while (state != Thread.State.TERMINATED){
Thread.sleep(100);
state = thread.getState();//更新线程状态
System.out.println(state);
}
}
}
5. 线程优先级
优先级低只是意味着获得调度的概率低，并不是优先级低就不会被调用了，这都是看CPU调度
* 线程的优先级用数字表示，范围从1~10
* Thread.MIN_PRIORITY = 1
* Thread.MAX_PRIORITY =10
* Thread.NORM_PRIORITY = 5
* 使用以下方式改变或者获取优先级
* getPriority()
* setPriority(int xxx)
package thread.state;
//测试线程的优先级
public class TestPriority {
public static void main(String[] args) {
//主线程优先级
System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
//创建线程
MyPriority myPriority = new MyPriority();
Thread t1 = new Thread(myPriority);
Thread t2 = new Thread(myPriority);
Thread t3 = new Thread(myPriority);
Thread t6 = new Thread(myPriority);
t1.setPriority(10);
t1.start();
t2.start();
t3.setPriority(8);
t3.start();
t6.setPriority(1);
t6.start();
}
}
class MyPriority implements Runnable{
@Override
public void run() {
System.out.println(Thread.currentThread().getName() + "-->" +Thread.currentThread().getPriority());
}
}
6. 守护（daemon）线程
* 线程分为用户线程和守护线程
* 虚拟机必须确保用户线程执行完毕（main）
* 虚拟机不用等待守护线程执行完毕，如后台记录操作日志，监控内存，垃圾回收等待（gc）
package thread.methods;
//测试守护线程
public class TestDaemon {
public static void main(String[] args) {
Love love = new Love();
You you = new You();
Thread thread = new Thread(love);
thread.setDaemon(true);//默认是false表示是用户线程
thread.start();//守护线程启动
new Thread(you).start();//用户线程启动
}
}
//守护线程
class Love implements Runnable{
@Override
public void run() {
while (true){
System.out.println("爱与你相伴");
}
}
}
//用户线程
class You implements Runnable{
@Override
public void run() {
for (int i = 0; i < 36500; i++) {
System.out.println("独行，相伴");
}
System.out.println("-====goodbye!world!====-");
}
}
7. 线程同步
并发：同一个对象被多个线程同时操作 形成条件：队列和锁（锁机制synchronized）
* 上万人同时抢100张票
* 两个银行同时取钱
7.1 三大不安全案例
package thread.syn;
//不安全的买票
//线程不安全，有负数
public class UnsafeBuyTicket {
public static void main(String[] args) {
BuyTicket buyTicket = new BuyTicket();
new Thread(buyTicket, "小明").start();
new Thread(buyTicket, "小红").start();
new Thread(buyTicket, "小杰").start();
}
}
class BuyTicket implements Runnable{
private int ticketNums = 10;
boolean flag = true;
public void run() {
while (flag){
if (ticketNums <= 1) flag = false;
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + " 拿到" + ticketNums--);
}
}
}
package thread.syn;
//银行取钱
public class UnsafeBank {
public static void main(String[] args) {
Account account = new Account(100000, "结婚基金");
Drawing you = new Drawing(account, 5000, "yourself");
Drawing yourWife = new Drawing(account, 10000, "yourWife");
you.start();
yourWife.start();
}
}
class Account{
int money;
String name;
public Account(int money, String name) {
this.money = money;
this.name = name;
}
}
class Drawing extends Thread{
Account account;
int drawingMoney;
int nowMoney;
public Drawing(Account account, int drawingMoney, String name){
super(name);
this.account = account;
this.drawingMoney = drawingMoney;
}
@Override
public void run() {
if (account.money - drawingMoney < 0){
System.out.println(this.getName()+ "余额不足");
return;
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money = account.money - drawingMoney;
nowMoney = nowMoney + drawingMoney;
System.out.println(account.name + "余额为" + account.money);
//Thread.currentThread().getName() == this.getName();
System.out.println(this.getName() + "手里的钱为" + nowMoney);
}
}
package thread.syn;
//表格
import java.util.ArrayList;
import java.util.List;
public class UnsafeList {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
for (int i = 0; i < 100000; i++) {
new Thread(()->{list.add(Thread.currentThread().getName());}).start();
}
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
7.2 同步方法
public synchronized void method(int args){} 同步方法的同步监听器就是this，即对象本身，或者是class
package thread.syn;
//安全的买票
public class UnsafeBuyTicket {
public static void main(String[] args) {
BuyTicket buyTicket = new BuyTicket();
new Thread(buyTicket, "小明").start();
new Thread(buyTicket, "小红").start();
new Thread(buyTicket, "小杰").start();
}
}
class BuyTicket implements Runnable{
private int ticketNums = 10;
boolean flag = true;
public void run() {
while (flag){
buy();
}
}
//synchronized 同步方法，锁的是this
private synchronized void buy() {
if (ticketNums <= 0) {flag = false;return;}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + " 拿到" + ticketNums--);
}
}
7.3 同步块
synchronized（Obj）{} Obj可以是任何对象，但是推荐使用共享资源（增删改）作为同步监视器
* 同步监视器的执行过程
* 第一个线程访问，锁定同步监视器，执行其中代码。
* 第二个线程访问，发现同步监视器被锁定，无法访问
* 第一个线程访问完毕，解锁同步监视器
* 第二线程访问，发现同步监视器没有锁，然后锁定并访问
package thread.syn;
public class UnsafeBank {
public static void main(String[] args) {
Account account = new Account(100000, "结婚基金");
Drawing you = new Drawing(account, 5000, "yourself");
Drawing yourWife = new Drawing(account, 10000, "yourWife");
you.start();
yourWife.start();
}
}
class Account{
int money;
String name;
public Account(int money, String name) {
this.money = money;
this.name = name;
}
}
class Drawing extends Thread{
Account account;
int drawingMoney;
int nowMoney;
public Drawing(Account account, int drawingMoney, String name){
super(name);
this.account = account;
this.drawingMoney = drawingMoney;
}
@Override
public void run() {
synchronized (account){
if (account.money - drawingMoney < 0){
System.out.println(this.getName()+ "余额不足");
return;
}
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
account.money = account.money - drawingMoney;
nowMoney = nowMoney + drawingMoney;
System.out.println(account.name + "余额为" + account.money);
//Thread.currentThread().getName() == this.getName();
System.out.println(this.getName() + "手里的钱为" + nowMoney);
}
}
}
package thread.syn;
import java.util.ArrayList;
import java.util.List;
public class UnsafeList {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
for (int i = 0; i < 100000; i++) {
new Thread(()->{
synchronized (list){
list.add(Thread.currentThread().getName());}
}).start();
}
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>(); 自带锁的list
package thread.syn;
import java.util.concurrent.CopyOnWriteArrayList;
//测试JUC安全类型的集合
public class TestJUC {
public static void main(String[] args) {
CopyOnWriteArrayList<String> list = new CopyOnWriteArrayList<String>();
for (int i = 0; i < 10000; i++) {
new Thread(()-> list.add(Thread.currentThread().getName())).start();
}
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(list.size());
}
}
7.4 死锁
死锁：某一个同步块同时拥有“两个以上对象的锁”
package thread.syn;
//死锁：多个线程互相抱着对方需要的资源，然后形成僵持
public class DeadLock {
public static void main(String[] args) {
MakeUp g1 = new MakeUp(0,"灰姑娘");
MakeUp g2 = new MakeUp(1,"白雪公主");
g1.start();
g2.start();
}
}
//口红
class LipStick{}
//镜子
class Mirror{}
class MakeUp extends Thread {
//需要的资源只有一份，用static来保证
static LipStick lipStick = new LipStick();
static Mirror mirror = new Mirror();
int choice;//选择
String name;//使用化妆品的人
MakeUp(int choice, String name) {
this.choice = choice;
this.name = name;
}
@Override
public void run() {
try {
makeup();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//化妆，互相持有对方的资源
private void makeup() throws InterruptedException {
if (choice == 0) {
synchronized (lipStick) {//获得口红的锁
System.out.println(this.name + "获得口红");
Thread.sleep(1000);
}
synchronized (mirror) {//获得镜子的锁
System.out.println(this.name + "获得镜子的锁");
}
} else {
synchronized (mirror) {//获得镜子的锁
System.out.println(this.name + "获得镜子的锁");
Thread.sleep(2000);
}
synchronized (lipStick) {//获得口红的锁
System.out.println(this.name + "获得口红的锁");
}
}
}
}
7.5 锁（显性LOCK）
package thread.syn;
import java.util.concurrent.locks.ReentrantLock;
public class TestLock {
public static void main(String[] args) {
TestLock2 testLock2 = new TestLock2();
new Thread(testLock2, "小明").start();
new Thread(testLock2, "小杰").start();
new Thread(testLock2, "小王").start();
}
}
class TestLock2 implements Runnable{
private int tickNums = 10;
boolean flag = true;
private final ReentrantLock reentrantLock = new ReentrantLock();
@Override
public void run() {
try{
reentrantLock.lock();
while (flag){
if (tickNums <= 0 ){
flag = false;
return;
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "获得了" + tickNums--);
}
}finally {
reentrantLock.unlock();
}
}
}
8. 线程协作
生产者消费者问题：生产者和消费者共享同一个资源，并且生产者和消费者之间相互依赖，互为条件
| 作用 | 方法名 |
|---|---|
| 表示线程一直等待，直到其他线程通知，与sleep不同，会释放锁 | wait（） |
| 指定等待的毫秒数 | wait(long timeout) |
| 唤醒一个等待状态的线程 | notify() |
| 唤醒同一个对象上所有调用wait()方法的线程，优先级别高的线程优先调度 | notifyAll() |
8.1 解决方式1
并发协作模型“生产者/消费者模式”-->管程法
* 生产者：负责生产数据的模块（可能是方法，对象，线程，进程）
* 消费者：负责处理数据的模块（可能是方法，对象，线程，进程）
* 缓冲区：消费者不能直接使用生产者的数据，他们之间有个“缓冲区”
生产者将生产好的数据放入缓冲区，消费者从缓冲区拿出数据
视频链接
package thread.itc;
//测试：生产者消费者模型-->管程法
public class TestPC {
public static void main(String[] args) {
SynContainer container = new SynContainer();
new Producer(container).start();
new Consumer(container).start();
}
}
//生产者
class Producer extends Thread{
SynContainer container;
public Producer(SynContainer container){
this.container = container;
}
//生产
@Override
public void run() {
for (int i = 1; i < 100; i++) {
container.push(new Chicken(i));
System.out.println("生产了" + i + "只鸡");
try {
Thread.sleep(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
//消费者
class Consumer extends Thread{
SynContainer container;
public Consumer(SynContainer container){
this.container = container;
}
//消费
@Override
public void run() {
for (int i = 1; i < 100; i++) {
System.out.println("消费了-->" + container.pop().id + "只鸡");
try {
Thread.sleep(0);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
//产品
class Chicken{
int id;
public Chicken(int id) {
this.id = id;
}
}
//缓冲区
class SynContainer{
//需要一个容器大小
Chicken[] chickens = new Chicken[10];
//容器计数器
int count = 0;
//生产者放入产品
public synchronized void push(Chicken chicken){
//如果容器满了，需要等待消费者消费
if(count == chickens.length){
//通知消费者消费，生产等待
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果没有满，丢入产品
chickens[count] = chicken;
count++;
//可以通知消费者消费产品
this.notifyAll();
}
//消费者消费产品
public synchronized Chicken pop(){
//判断能否消费
if (count == 0){
//等待生产者生产
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
//如果可以消费
count--;
Chicken chicken = chickens[count];
//吃完了，通知生产者生产
this.notifyAll();
return chicken;
}
}
8.2 解决方式2
并发协作模型“生产者/消费者模式”-->信号灯法
package thread.itc;
////测试：生产者消费者模型-->信号灯法
public class TestPC2 {
public static void main(String[] args) {
Program program = new Program();
new Player(program).start();
new Audience(program).start();
}
}
//生产者-->演员
class Player extends Thread{
Program program;
public Player(Program program){
this.program = program;
}
@Override
public void run() {
for (int i = 1; i < 20; i++) {
this.program.show ("Jay's专场", i);
}
}
}
//消费者-->观众
class Audience extends Thread{
Program program;
public Audience(Program program){
this.program = program;
}
@Override
public void run() {
for (int i = 1; i < 20; i++) {
this.program.clap();
}
}
}
//产品-->节目
class Program{
//演员表演，观众观看 T
//观众鼓掌，演员致敬 F
String name;//表演的节目
int order;//节目序号
boolean flag = true;//信号灯
//表演
public synchronized void show (String name, int order){
if(!flag){
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("演员表演了" + name + "第" + order + "个节目");
//观众鼓掌喝彩，演员致敬
this.notifyAll();
this.name = name;
this.order = order;
this.flag = !this.flag;
}
//鼓掌
public synchronized void clap(){
if (flag){
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("观众看完" + name + "第" + order + "个节目，会场响起热烈掌声，演员们鞠躬致敬");
this.notifyAll();
this.flag = !this.flag;
}
}
9. 线程池
* 背景：经常创建和销毁、使用量特别大的资源，比如并发情况下的线程，对性能影响很大
* 思路：提前创建好多个线程，放到线程池中，使用时直接获取，使用完放回池中。可以避免繁创建销毁、实现重复利用。类似生活中的公共交通工具（单车）。
* 好处：
* 提高响应速度（减少了创建新线程的时间）
* 降低资源消耗（重复利用线程池中线程，不用每次都创建）
* 便于线程管理
newFixedThreadPool：线程池大小
corePoolSize：核心池的大小
maximumPoolSize：最大线程数
keepAliveTime：线程没有任务时最多保持多长时间后会终止
线程池相关API：ExecutorService 和 Executors
void execute(Runnable command)：执行任务/命令，没有返回值，一般用来执行Runnable
<T>Future<T>submit(Callable<T>task)：执行任务，有返回值，一般用来执行
Callablevoid shutdown()：关闭连接池
Executors：工具类、线程池的工厂类，用于创建并返回不同类型的线程池
package thread.syn;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
//测试线程池
public class TestPool {
public static void main(String[] args) {
//1.创建线程池
ExecutorService service = Executors.newFixedThreadPool(10);
service.execute(new MyThread());
service.execute(new MyThread());
service.execute(new MyThread());
service.execute(new MyThread());
//2.关闭连接
service.shutdown();
}
}
class MyThread implements Runnable{
@Override
public void run() {
for (int i = 0; i < 5; i++) {
System.out.println(Thread.currentThread().getName() + " " + i);
}
}
}
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