线程优先级 线程优先级Java提供一个线程调度器来监控程序中启动后进入就绪状态的所有线程，线程调度按照优先级来调度执行线程优先级范围：1~10Thread.MIN_PRIORITY = 1Thread.MAX_PRIORITY = 10设置方法注：1、线程优先级应先设置再启动​ 2、优先级低只意味着获得调度的概率低，并不是优先级低就不会被调用，最终结果由CPU调度决定package com.thread.state; /** * @Author suaxi * @Date 2020/11/26 11:11 * 测试线程优先级 */ public class TestPriority { public static void main(String[] args) { //主线程默认优先级 System.out.println(Thread.currentThread().getName()+"---->"+Thread.currentThread().getPriority()); //设置优先级 Mypeiority mypeiority = new Mypeiority(); Thread t1 = new Thread(mypeiority); Thread t2 = new Thread(mypeiority); Thread t3 = new Thread(mypeiority); Thread t4 = new Thread(mypeiority); Thread t5 = new Thread(mypeiority); //先设置，再启动 t1.start(); t2.setPriority(3); t2.start(); t3.setPriority(Thread.MAX_PRIORITY); //MAX_PRIORITY=10 t3.start(); t4.setPriority(Thread.MIN_PRIORITY); t4.start(); t5.setPriority(7); t5.start(); } } class Mypeiority implements Runnable{ @Override public void run() { System.out.println(Thread.currentThread().getName()+"---->"+Thread.currentThread().getPriority()); } }

线程礼让 线程礼让Thread.yield();实例：package com.thread.state; /** * @Author suaxi * @Date 2020/11/25 21:31 */ 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(); System.out.println(Thread.currentThread().getName()+"线程执行结束"); } }注：礼让的结果最终由CPU调度决定

线程休眠 线程休眠sleep(时间)指当前线程阻塞的毫秒数sleep存在异常InterruptedExceptionsleep时间达到后线程进入就绪状态可以模拟网络延时，倒计时等每一个对象都有一个锁，sleep不会释放锁模拟倒计时实例：package com.thread.state; import java.text.SimpleDateFormat; import java.util.Date; /** * @Author suaxi * @Date 2020/11/25 17:24 */ public class TestSleep2 { public static void main(String[] args){ //tenDown(); //打印当前系统时间 Date date = new Date(System.currentTimeMillis()); while (true){ try { Thread.sleep(1000); System.out.println(new SimpleDateFormat("HH:mm:ss").format(date)); date = new Date(System.currentTimeMillis()); //更新当前系统时间 } catch (InterruptedException e) { e.printStackTrace(); } } } //模拟倒计时 public static void tenDown() throws InterruptedException { int num = 10; while (true){ Thread.sleep(1000); System.out.println(num--); if (num<=0){ break; } } } }

线程状态 线程状态

多线程 Process（进程）：程序是指令和数据的有序集合，其本身没有任何运行的含义，是一个静态的概念进程是执行程序的一次执行过程，它是一个动态的概念，是系统资源分配的单位一个进程中至少有一个线程，也可以包含若干个线程很多多线程是模拟出来的，真正的多线程是指有多个cpu，即多核。如果是模拟出来的多线程，即在单个cpu的情况下，在同一个时间点，cpu只能执行一个代码，因为切换得很快，所以就有同时执行的错觉Thread（线程）：线程是独立执行的路径在程序运行时，即使没有自己创建线程，后台也会有多个线程，如主线程，gc线程main()称之为主线程，为系统的入口，用于执行整个程序在一个进程中如果开辟了多个线程，线程的运行由调度器安排调度，调度器是与操作系统紧密相关的，其执行的先后顺序不能人为干预对同一份资源操作时，会存在资源抢夺的问题，需要加入并发控制线程会带来额外的开销，如cpu调度时间，并发控制开销等每个线程在自己的工作内存交互，内存控制不当会造成数据不一致普通方法调用和多线程调用run()方法：只有主线程一条执行路径调用start()方法：多条执行路径，主线程和子线程并行交替执行小结1、继承Thread类子类继承Thread类具备多线程能力启动线程：子类对象.start()不建议使用：避免OOP单继承局限性2、实现Runnable接口实现接口Runnable具有多线程能力启动线程：传入目标对象+Thread对象.start()推荐使用：避免单继承局限性，灵活方便，方便同一个对象被多个线程使用//一份资源 TestThread t = new TestThread(); //多个代理 new Thread(t1,"多线程测试01").start(); new Thread(t1,"多线程测试02").start(); new Thread(t1,"多线程测试03").start();3、实现Callable接口实现Callable接口，需要返回值类型重写call方法，需要抛出异常创建目标对象创建执行服务：ExecutorService ser = Executors.newFixedThreadPool(3); //3为线程池数量提交执行：Future result = ser.submit();获取结果：Boolean rs1 = result.get();关闭服务：ser.shutdownNow();

Lambda表达式 Lambda表达式（Jdk1.8之后出现）λ希腊字母，英文名称为Lambda避免匿名内部类定义过多其本质是函数式编程(params) ->expression[表达式] (params) ->statement[语句] (params) ->{statement}例：a->System.out.println("Lambda表达式测试-->"+a);new Thread(()-> System.out.println("Lambda表达式测试")).start();简化步骤实例：定义函数式接口，实现类--->静态内部类--->局部内部类--->匿名内部类（逐步简化）package com.lambda.demo01; /** * @Author suaxi * @Date 2020/11/25 11:21 */ public class TestLambda01 { //3、静态内部类 static class Like2 implements ILike{ @Override public void lambda() { System.out.println("I like lambda2"); } } public static void main(String[] args) { ILike like = new Like(); like.lambda(); like = new Like2(); like.lambda(); //4、局部内部类 class Like3 implements ILike{ @Override public void lambda() { System.out.println("I like lambda3"); } } like = new Like3(); like.lambda(); //5、匿名内部类,没有类的名称，必须借助接口 like = new ILike() { @Override public void lambda() { System.out.println("I like lambda4"); } }; like.lambda(); //6、用lambda简化 like = ()->{ System.out.println("I like lambda5"); }; like.lambda(); } } //1、定义一个函数式接口 interface ILike{ void lambda(); } //2、实现类 class Like implements ILike{ @Override public void lambda() { System.out.println("I like lambda1"); } }Lambda表达式总结:package com.lambda.demo01; /** * @Author suaxi * @Date 2020/11/25 16:24 */ public class TestLambda02 { public static void main(String[] args) { DisLike disLike = null; /*//1、lambda表达式简化 DisLike disLike = (int a) ->{ System.out.println("lambda表达式测试"+a); }; //简化1：参数类型 disLike = (a) ->{ System.out.println("lambda表达式测试"+a); }; //简化2：简化括号 disLike = a -> { System.out.println("lambda表达式测试"+a); }; //简化3：去掉花括号 disLike = a -> System.out.println("lambda表达式测试"+a); disLike.dlike(1);*/ //多个参数时 disLike = (a,b) ->{ System.out.println("lambda表达式测试"+a); System.out.println("lambda表达式测试"+b); }; disLike.dlike(1,2); //总结： //1、lambda表达式只有在一行代码的情况下才能简化为一行，如果有多行，则需用代码块包裹 //2、函数式接口是前提 //3、多个参数也可以去掉参数类型（要去掉就都去掉），有多个参数的时候不能像简化3一样去掉括号， // 单个参数时可以简化括号，多个参数时必须加上括号 } } interface DisLike{ void dlike(int a,int b); }

UDP 类似于发短信，不用连接，只需要知道接收端的地址发送消息发送端package com.network.lesson03; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; /** * @Author suaxi * @Date 2020/11/23 11:03 * UDP发送消息，不需要连接服务器 */ public class UpdClientDemo01 { public static void main(String[] args) throws Exception { //1、建立一个socket DatagramSocket datagramSocket = new DatagramSocket(); //2、建立包 String mgs = "故乡的樱花开了！"; InetAddress localhost = InetAddress.getByName("localhost"); int port = 8888; //数据 数据的长度起始 要发送给谁 DatagramPacket datagramPacket = new DatagramPacket(mgs.getBytes(), 0, mgs.length(),localhost,port); //3、发送包 datagramSocket.send(datagramPacket); //4、关闭流 datagramSocket.close(); } } 接收端package com.network.lesson03; import java.net.DatagramPacket; import java.net.DatagramSocket; /** * @Author suaxi * @Date 2020/11/23 11:18 * UDP接收端，还是要等待客户端的连接 */ public class UpdServerDemo01 { public static void main(String[] args) throws Exception { //开放端口 DatagramSocket datagramSocket = new DatagramSocket(8888); //接收数据包 byte[] bytes = new byte[1024]; DatagramPacket datagramPacket = new DatagramPacket(bytes, 0, bytes.length); datagramSocket.receive(datagramPacket); //阻塞接收 System.out.println(datagramPacket.getAddress().getHostAddress()); //接收地址 System.out.println(new String(datagramPacket.getData(),0,datagramPacket.getLength())); //数据包消息 //关闭连接 datagramSocket.close(); } } 循环发送消息package com.network.chat; import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetAddress; import java.net.InetSocketAddress; /** * @Author suaxi * @Date 2020/11/23 11:34 * 发送消息 */ public class UdpSenderDemo01 { public static void main(String[] args) throws Exception { DatagramSocket datagramSocket = new DatagramSocket(8888); //准备数据，控制台读取输入的数据System.in BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); while (true){ String data = bufferedReader.readLine(); byte[] bytes = data.getBytes(); DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length, new InetSocketAddress("localhost", 8889)); datagramSocket.send(packet); if (data.equals("bye")){ break; } } datagramSocket.close(); } } package com.network.chat; import java.net.DatagramPacket; import java.net.DatagramSocket; /** * @Author suaxi * @Date 2020/11/23 11:34 * UDP聊天咨询Demo（循环接收） */ public class UdpReciverDemo01 { public static void main(String[] args) throws Exception { DatagramSocket datagramSocket = new DatagramSocket(8889); while (true){ //准备接收包裹 byte[] bytes = new byte[1024]; DatagramPacket datagramPacket = new DatagramPacket(bytes, 0, bytes.length); datagramSocket.receive(datagramPacket); //阻塞式接收包裹 byte[] data = datagramPacket.getData(); String reciveData = new String(data, 0, data.length); System.out.println(reciveData); //断开连接 if (reciveData.equals("bye")){ break; } } datagramSocket.close(); } } 在线咨询，两者都是发送方，也都可以是接收方发送端package com.network.chat; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.InetSocketAddress; import java.net.SocketException; /** * @Author suaxi * @Date 2020/11/23 14:37 */ public class TalkSend implements Runnable{ DatagramSocket datagramSocket = null; BufferedReader bufferedReader = null; private int fromPort; private String toIP; private int toPort; public TalkSend(int fromPort, String toIP, int toPort) { this.fromPort = fromPort; this.toIP = toIP; this.toPort = toPort; try { datagramSocket = new DatagramSocket(fromPort); bufferedReader = new BufferedReader(new InputStreamReader(System.in)); } catch (SocketException e) { e.printStackTrace(); } } @Override public void run() { while (true){ try { String data = bufferedReader.readLine(); byte[] bytes = data.getBytes(); DatagramPacket packet = new DatagramPacket(bytes, 0, bytes.length, new InetSocketAddress(this.toIP, this.toPort)); datagramSocket.send(packet); if (data.equals("bye")){ break; } } catch (IOException e) { e.printStackTrace(); } } datagramSocket.close(); } } 接收端package com.network.chat; import java.io.IOException; import java.net.DatagramPacket; import java.net.DatagramSocket; import java.net.SocketException; /** * @Author suaxi * @Date 2020/11/23 14:43 */ public class TalkRecive implements Runnable{ DatagramSocket datagramSocket = null; private int port; private String mgsFrom; public TalkRecive(int port,String mgsFrom) { this.port = port; this.mgsFrom = mgsFrom; try { datagramSocket = new DatagramSocket(port); } catch (SocketException e) { e.printStackTrace(); } } @Override public void run() { while (true){ try { //准备接收包裹 byte[] bytes = new byte[1024]; DatagramPacket datagramPacket = new DatagramPacket(bytes, 0, bytes.length); datagramSocket.receive(datagramPacket); //阻塞式接收包裹 byte[] data = datagramPacket.getData(); String reciveData = new String(data, 0, data.length); System.out.println(mgsFrom+":"+reciveData); //断开连接 if (reciveData.equals("bye")){ break; } } catch (IOException e) { e.printStackTrace(); } } datagramSocket.close(); } } 具体实现：package com.network.chat; /** * @Author suaxi * @Date 2020/11/23 14:46 */ public class TalkStudent { public static void main(String[] args) { //开启两个线程 new Thread(new TalkSend(7777,"localhost",8888)).start(); new Thread(new TalkRecive(9999,"老师")).start(); } } package com.network.chat; /** * @Author suaxi * @Date 2020/11/23 14:48 */ public class TalkTeacher { public static void main(String[] args) { new Thread(new TalkSend(7778,"localhost",9999)).start(); new Thread(new TalkRecive(8888,"学生")).start(); } }

通信协议 网络通信协议：速率，传输码率，代码结构，传输控制……TCP/IP协议簇（实际上是一组协议）TCP：用户传输协议UDP：用户数据报协议TCP与UDP对比：TCP：连接、稳定三次握手，四次挥手最少需要三次，保证稳定链接 A：咋地! B：干啥？ A：干一架 A：我要走了 B：你要走了吗 B：你真的要走了吗 A：走了客户端、服务端传输完成，释放连接。效率低UDP：不连接，不稳定客户端、服务端：没有明确的界限不管有没有准备好，都可以发给你DDOS（饱和攻击）TCP客户端：1、连接服务器socket2、发送消息package com.network.lesson02; import java.io.IOException; import java.io.OutputStream; import java.net.InetAddress; import java.net.Socket; import java.net.UnknownHostException; /** * @Author suaxi * @Date 2020/11/20 17:37 * 客户端 */ public class TcpClientDemo01 { public static void main(String[] args) { Socket socket = null; OutputStream os = null; //1、要知道服务器的地址、端口号 try { InetAddress serverIp = InetAddress.getByName("127.0.0.1"); int port = 8888; //2、创建一个socke连接 socket = new Socket(serverIp, port); //3、发送消息、IO流 os = socket.getOutputStream(); os.write("故乡的樱花开了".getBytes()); } catch (Exception e) { e.printStackTrace(); }finally { if (os!=null){ try { os.close(); } catch (IOException e) { e.printStackTrace(); } } if (socket!=null){ try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } } } 服务器1、建立服务端口ServerSocket2、等待用户连接3、接收客户端发送的消息（管道流）package com.network.lesson02; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.ServerSocket; import java.net.Socket; /** * @Author suaxi * @Date 2020/11/20 17:38 * 服务端 */ public class TcpServerDemo01 { public static void main(String[] args) { ServerSocket serverSocket = null; Socket socket = null; InputStream is = null; ByteArrayOutputStream baos = null; try { //1、建立服务器地址 serverSocket = new ServerSocket(8888); while (true){ //2、等待客户端连接 socket = serverSocket.accept(); //3、读取客户端消息 is = socket.getInputStream(); //管道流 baos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int length; while ((length=is.read(buffer))!=-1){ baos.write(buffer,0,length); } System.out.println(baos); } } catch (IOException e) { e.printStackTrace(); }finally { if (baos!=null){ try { baos.close(); } catch (IOException e) { e.printStackTrace(); } } if (is!=null){ try { is.close(); } catch (IOException e) { e.printStackTrace(); } } if (socket!=null){ try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } if (serverSocket!=null){ try { serverSocket.close(); } catch (IOException e) { e.printStackTrace(); } } } } } 文件上传服务端package com.network.lesson02; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.ServerSocket; import java.net.Socket; /** * @Author suaxi * @Date 2020/11/22 11:26 * 文件上传服务端 */ public class TcpServerDemo02 { public static void main(String[] args) throws IOException { //1、创建服务 ServerSocket serverSocket = new ServerSocket(8889); //2、监听客户端的连接 Socket socket = serverSocket.accept();//阻塞式监听，会一直等待客户端连接 //3、获取输入流 InputStream is = socket.getInputStream(); //4、文件输出 FileOutputStream fileOutputStream = new FileOutputStream("recive.jpg"); byte[] bytes = new byte[1024]; int length; while ((length=is.read(bytes))!=-1){ fileOutputStream.write(bytes,0,length); } //通知客户端文件接收完毕 OutputStream os = socket.getOutputStream(); os.write("文件上传成功！".getBytes()); //5、关闭资源 fileOutputStream.close(); is.close(); socket.close(); serverSocket.close(); } } 客户端package com.network.lesson02; import java.io.*; import java.net.InetAddress; import java.net.Socket; /** * @Author suaxi * @Date 2020/11/22 11:26 * 文件上传客户端 */ public class TcpClientDemo02 { public static void main(String[] args) throws Exception { //1、创建一个socket连接 Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),8889); //2、创建一个输出流 OutputStream os = socket.getOutputStream(); //3、读取文件 FileInputStream fileInputStream = new FileInputStream(new File("test.jpg")); //4、写出文件 byte[] bytes1 = new byte[1024]; int length1; while((length1=fileInputStream.read(bytes1))!=-1){ os.write(bytes1,0,length1); } //通知服务器已经上传完毕 socket.shutdownOutput(); //确定服务器接收完毕，才断开连接 InputStream inputStream = socket.getInputStream(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); byte[] bytes2 = new byte[1024]; int length2; while ((length2=inputStream.read(bytes2))!=-1){ baos.write(bytes2,0,length2); } System.out.println(baos.toString()); //5、关闭资源 baos.close(); inputStream.close(); fileInputStream.close(); os.close(); socket.close(); } }