JAVA自学笔记（9）——网络通信、函数式接口

TCP通信

1.0 客户端的实现

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

public class TCPSocket {
    public static void main(String[] args) throws IOException {
        Socket socket=new Socket("127.0.0.1",8888);
        OutputStream stream = socket.getOutputStream();
        stream.write("你好服务器".getBytes());
        InputStream inputStream = socket.getInputStream();
        byte []bytes=new byte[1024];
        int read = inputStream.read(bytes);
        System.out.println(new String(bytes,0,read));

        socket.close();
    }
}

　　

2.0 服务器代码实现

 

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket=new ServerSocket( 8888 );
        Socket socket = serverSocket.accept();
        InputStream stream = socket.getInputStream();
        byte bytes[]=new byte[1024];
        int read = stream.read(bytes);
        System.out.println(new String(bytes,0,read));

        OutputStream outputStream = socket.getOutputStream();
        outputStream.write("谢谢收到！".getBytes());
        socket.close();
        serverSocket.close();

    }
}

　　

 3.0 TCP通信的综合案例（上传文件从客户端到服务器，并且存储到服务器的硬盘中）

客户端实现

import java.io.*;
import java.net.Socket;

public class TCPSocket {
    public static void main(String[] args) throws IOException {
        FileInputStream fis=new FileInputStream("D:\photos\白雪公主.jpg");
        Socket socket=new Socket("127.0.0.1",8888);
        OutputStream outputStream = socket.getOutputStream();
        byte []bytes=new byte[1024];
        int len=0;
        while((len=fis.read(bytes))!=-1)
        {
            outputStream.write(bytes,0,len);
        }
        socket.shutdownOutput();
        /*
        *上传完文件，给服务器写一个结束标记
        * 禁用此套接字的输出流
        * 对于TCP套接字，任何之前的写入的数据都将被发送，
        * 并且后跟TCP的正常连接终止序列
        * */

        InputStream inputStream = socket.getInputStream();
        byte []bytes1=new byte[1024];
        int len1=inputStream.read(bytes1);
        System.out.println(new String(bytes1,0,len1));
        socket.close();
        fis.close();
    }
}

　　

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class TCPServer{
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket=new ServerSocket(8888);
        Socket socket = serverSocket.accept();
        InputStream inputStream = socket.getInputStream();
        File file=new File("D:\upload");
        if(!file.exists())
        {
            file.mkdirs();
        }
        FileOutputStream fos=new FileOutputStream(file+"\白雪公主.jpg") ;

        byte[] bytes=new byte[1024];
        int len=0;
        while((len=inputStream.read(bytes))!=-1)
        {
            fos.write(bytes,0,len);
        }
        socket.getOutputStream().write("上传成功！".getBytes());
        serverSocket.close();
        fos.close();
        socket.close();
    }
}

函数式接口

1.0 概念

2.0利用Lambda表达式的执行延迟（接口作为方法的参数传递）

优化日志的案例（输入编号，输出字符串拼接后的字符串 先字符串拼接后执行 所以可能会浪费资源）

public interface MessageBuilder {
    public abstract String bulidMessage();
}

　　

public class Main{
    public static void main(String[] args) {
        String msg1="Hello";
        String msg2="World";
        String msg3="Java";
        showlog(1,()->msg1+msg2+msg3
        );
}

    private static void showlog(int grade,MessageBuilder ms) {
        if(grade==1)
        {
            System.out.println(ms.bulidMessage());
        }

    }
    }

3.0 接口作为方法的返回值传递

数组排序案例

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Main{
    public static Comparator<String> getCompare()
{
     return new Comparator<String>() {
         @Override
         public int compare(String o1, String o2) {
             return o2.length()-o1.length();//长度降序
         }
     };
}
    public static void main(String[] args) {
        String arr[]={"jin,27","jimin,25","v,25"};
        Arrays.sort(arr,(o1,o2)->o2.length()-o1.length());
        System.out.println(Arrays.toString(arr));
    }
}

打印结果：

[jimin,25, jin,27, v,25]

常用的函数式接口

1.0 Supplier接口

练习 找出数组中的最大值 并打印

import java.util.function.Supplier;

public class Main{
    public static int getMax(Supplier<Integer> sup)
    {
        Integer integer = sup.get();
        return  integer;
    }
    public static void main(String[] args) {
        int Max = getMax(() -> {
            int arr[] = {34, 234, 52, 5, 65};
            int max = arr[0];
            for (int i : arr) {
                if (i > max) max = i;
            }
            return max;
        });
        System.out.println(Max);//234

    }
}

2.0 Consumer接口

import java.util.function.Consumer;

public class Main {
    public static void conSume(String name, Consumer<String> con)
    {
        con.accept(name);
    }
    public static void main(String[] args) {
    conSume("金泰亨",(name)->{
        System.out.println(name);
    });
    }
}

默认方法 andThen

练习 格式化打印信息 格式 姓名：XX，年龄：XX

import java.util.function.Consumer;

public class Main {
    public static void conSume(String []arr, Consumer<String> con1,Consumer<String> con2)
    {

        for (String s : arr) {
            con1.andThen(con2).accept(s);
        }
    }
    public static void main(String[] args) {
        String arr[]={"Suga,26","Jimin,25","JK,23"};
        conSume(arr,(s)->{
            String s1 = s.split(",")[0];
            System.out.print("姓名："+s1+",");

        },(s)->{
            String s2 = s.split(",")[1];
            System.out.println("年龄："+s2);
        });
    }

}

打印结果：

姓名：Suga,年龄：26
姓名：Jimin,年龄：25
姓名：JK,年龄：23

3.0 predicate接口

基本使用

import java.util.function.Predicate;

public class Main{
    public static void CheckString(String s, Predicate<String> pre)
{
    System.out.println(pre.test(s));//false
}
    public static void main(String[] args) {
       String s="abcde";
       CheckString(s,(str)->{
           return s.length()>5;
       });
    }
}

默认方法 and

import java.util.function.Predicate;

public class Main{
    public static void checkString(String s, Predicate<String> pre1,Predicate<String> pre2)
    {
        boolean test = pre1.and(pre2).test(s);
        System.out.println(test);
    }
    public static void main(String[] args) {
        String s="abcdef";
        checkString(s,(str)->
            str.length()>5
        ,(str)->str.contains("a")
        );
    }
}

默认方法 or

 

默认方法 negate

4.0 Function接口

练习将String->Integer+10   Integer->String 

import java.util.function.Function;

public class Main{
    public static void Method(String s, Function<String,Integer> fun1,Function<Integer,String> fun2)
    {
        String apply = fun1.andThen(fun2).apply(s);
        System.out.println(apply);
    }
    public static void main(String[] args) {
       String s="23";
       Method(s,(str)->{
           int i = Integer.parseInt(s);
           return i+10;
       },(i)->{
        return i+"";
       });
    }
}