为什么我的else if代码不在服务器端运行？我想让输入打印给定的次数循环在客户端运行

Question

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

public class MyServer {  
    public static void main(String[] args){  
        try{  
            ServerSocket ss=new ServerSocket(5001);  
            Socket s=ss.accept();//establishes connection   
            DataInputStream dis=new DataInputStream(s.getInputStream());  
            String  str=(String)dis.readUTF();  
            System.out.println("message= "+str);  

            DataOutputStream dout=new DataOutputStream(s.getOutputStream());  
            if ("Hi".equals(str)){
                dout.writeUTF("How are you?");
            } else if ("Bye".equals(str)){
                dout.writeUTF("Thankyou! Have a Good day!"); 
            } **else if (str != null)){
                try {
                    String numbers;
                    numbers = str.replaceAll("[^0-9]", ""); 
                    int number = Integer.parseInt(numbers);
                     dout.writeUTF("The line is being printed"); 
                    for (int i = 0; i < number; i++) {
                            dout.writeUTF(str.replaceAll("[^a-z,^A-Z]", ""));
                    }
                } catch (Exception e) {
                    //TODO: handle exception
                }**
                
                 
            } else {
                dout.writeUTF("Sorry!");
            }       
            dout.flush();  
            dout.close();  
            s.close();  
            ss.close();  
        } catch(Exception e) {
            System.out.println(e);
        } 
    }  
}  

import java.io.*;  
import java.net.*;  
import java.util.*;  

public class MyClient {  
    public static void main(String[] args) {  
        try{
            Scanner sc = new Scanner(System.in);  
            Socket s=new Socket("localhost",5001);  
            DataOutputStream dout=new DataOutputStream(s.getOutputStream());
            String str1= sc.nextLine();           
            dout.writeUTF(str1);  
            dout.flush(); 
            
            DataInputStream dis=new DataInputStream(s.getInputStream());  
            String  str=(String)dis.readUTF(); 
            System.out.println("message= "+str);

            dout.close();  
            dis.close();
            s.close();  
        } catch(Exception e) {
            System.out.println(e);} 
    }  
} 

我从客户端向服务器提供输入，并希望该输入在客户端打印多次。但做不到。谁能让我知道我在这里犯了什么错误？它正在回复消息“嗨”和“再见”，其他一切都很好。

Answer 1

以下是您的代码和我的更正。
（代码后面的注释。）

类MyServer

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class MyServer {
    public static void main(String[] args) {
        try (ServerSocket ss = new ServerSocket(5001)) {
            Socket s = ss.accept();// establishes connection
            InputStream is = s.getInputStream();
            int count = is.available();
            while (count <= 0) {
                try {
                    Thread.sleep(1000L);
                    System.out.println("'MyServer' is sleeping (for one second)...");
                }
                catch (InterruptedException xInterrupted) {
                    // Ignore.
                }
                count = is.available();
            }
            DataInputStream dis = new DataInputStream(is);
            String str = dis.readUTF();
            System.out.println("message= " + str);
            DataOutputStream dout = new DataOutputStream(s.getOutputStream());
            if ("Hi".equals(str.trim())) {
                dout.writeUTF("How are you?");
            }
            else if ("Bye".equals(str)) {
                dout.writeUTF("Thankyou! Have a Good day!");
            }
            else if (str != null) {
                try {
                    String numbers;
                    numbers = str.replaceAll("[^0-9]", "");
                    int number = Integer.parseInt(numbers);
                    dout.writeUTF("The line is being printed");
                    for (int i = 0; i < number; i++) {
                        dout.writeUTF(str.replaceAll("[^a-z,^A-Z]", ""));
                    }
                    dout.flush();
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
            }
            dout.flush();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        try {
            Thread.sleep(2000L);
        }
        catch (InterruptedException xInterrupted) {
            // Ignore.
        }
    }
}

类MyClient

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;
import java.util.Scanner;

public class MyClient {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str1 = sc.nextLine();
        try (Socket s = new Socket("localhost", 5001);
             DataOutputStream dout = new DataOutputStream(s.getOutputStream());
             DataInputStream dis = new DataInputStream(s.getInputStream())) {
            dout.writeUTF(str1);
            dout.flush();
            try {
                Thread.sleep(500L);
            }
            catch (InterruptedException xInterrupted) {
                // Ignore.
            }
            String str = dis.readUTF();
            System.out.println("message= " + str);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
}