JAVA自學筆記（9）——網絡通訊、函數式接口

時間 2020-07-13

標籤 java 自學筆記網絡通訊函數接口欄目 Java 简体版

原文原文鏈接

TCP通訊

1.0 客戶端的實現java

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("你好服務器".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 服務器代碼實現數組

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("謝謝收到！".getBytes());
        socket.close();
        serverSocket.close();

    }
}

3.0 TCP通訊的綜合案例（上傳文件從客戶端到服務器，而且存儲到服務器的硬盤中）服務器

客戶端實現app

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();
        /*
        *上傳完文件，給服務器寫一個結束標記
        * 禁用此套接字的輸出流
        * 對於TCP套接字，任何以前的寫入的數據都將被髮送，
        * 而且後跟TCP的正常鏈接終止序列
        * */

        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("上傳成功！".getBytes());
        serverSocket.close();
        fos.close();
        socket.close();
    }
}

函數式接口

1.0 概念socket

2.0利用Lambda表達式的執行延遲（接口做爲方法的參數傳遞）ide

優化日誌的案例（輸入編號，輸出字符串拼接後的字符串先字符串拼接後執行因此可能會浪費資源）函數

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 接口做爲方法的返回值傳遞優化

數組排序案例ui

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();//長度降序
         }
     };
}
    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));
    }
}

打印結果：spa

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

經常使用的函數式接口

1.0 Supplier接口

練習找出數組中的最大值並打印

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);
    });
    }
}

默認方法 andThen

練習格式化打印信息格式姓名：XX，年齡：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("年齡："+s2);
        });
    }

}

打印結果：

姓名：Suga,年齡：26
姓名：Jimin,年齡：25
姓名：JK,年齡：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;
       });
    }
}

默認方法 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")
        );
    }
}

默認方法 or

默認方法 negate

4.0 Function接口

練習將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+"";
       });
    }
}