host != null ? new InetSocketAddress(host, port) : new InetSocketAddress(InetAddress.getByName(null)三步操作符什么意思

这是一个三目运算符，也叫条件运算符，它有三个操作数。它的语法是：

condition ? expression1 : expression2

它的含义是如果条件(condition)成立，就返回expression1的值，否则返回expression2的值。

在这个代码片段中，条件为host不为null，如果host不为null，则返回一个以host和port为参数的InetSocketAddress对象；如果host为null，则返回一个以本地主机地址为参数的InetSocketAddress对象。这个三目运算符的作用是根据host是否为null来选择返回的InetSocketAddress对象。

相关问题

优化一下代码package Y; import java.io.*; import java.net.*; import java.util.*; public class Shiyan5Client { public static void main(String[] args) { Scanner sc = new Scanner(System.in); Socket mysocket = null; DataInputStream in = null; DataOutputStream out = null; Thread timeData; TellTime time = null; try { mysocket = new Socket(); time = new TellTime(); timeData = new Thread(time); System.out.println("输入服务器IP:"); String IP = sc.nextLine(); System.out.println("输入端口号:"); int port = sc.nextInt(); if (mysocket.isConnected()) {} else { InetAddress address = InetAddress.getByName(IP); InetSocketAddress socketAddress = new InetSocketAddress(IP, port); mysocket.connect(socketAddress); in = new DataInputStream(mysocket.getInputStream()); out = new DataOutputStream(mysocket.getOutputStream()); time.setDataInputStream(in); timeData.start(); } } catch (Exception e) { System.out.println("服务器已断开:"+e); // TODO: handle exception } System.out.println("请输入服务:"); while (sc.hasNext()) { try { String service = sc.next(); out.writeUTF(service); } catch (Exception e) { // TODO: handle exception } } } }

可以尝试对代码进行以下优化：

1. 将输入输出流的初始化放在连接成功时进行，而非在Socket创建时进行，这样可以避免在连接失败时无法关闭输入输出流的情况。

2. 对于Thread的启动，建议使用ExecutorService来管理，这样可以更好地控制线程的启动和关闭。

3. 在异常处理中，可以添加一些具体的处理逻辑，比如关闭Socket等资源，避免资源泄露。

下面是优化后的代码：

package Y;

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Shiyan5Client {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Socket mysocket = null;
        DataInputStream in = null;
        DataOutputStream out = null;
        ExecutorService executor = Executors.newSingleThreadExecutor();
        TellTime time = null;

        try {
            System.out.println("输入服务器IP:");
            String IP = sc.nextLine();
            System.out.println("输入端口号:");
            int port = sc.nextInt();

            mysocket = new Socket();
            InetAddress address = InetAddress.getByName(IP);
            InetSocketAddress socketAddress = new InetSocketAddress(address, port);
            mysocket.connect(socketAddress);

            in = new DataInputStream(mysocket.getInputStream());
            out = new DataOutputStream(mysocket.getOutputStream());
            time = new TellTime();
            time.setDataInputStream(in);
            executor.execute(time);
        } catch (Exception e) {
            System.out.println("服务器已断开:" + e);
            // TODO: handle exception
            if (mysocket != null) {
                try {
                    mysocket.close();
                } catch (IOException ioException) {
                    ioException.printStackTrace();
                }
            }
            if (in != null) {
                try {
                    in.close();
                } catch (IOException ioException) {
                    ioException.printStackTrace();
                }
            }
            if (out != null) {
                try {
                    out.close();
                } catch (IOException ioException) {
                    ioException.printStackTrace();
                }
            }
            executor.shutdown();
        }

        System.out.println("请输入服务:");
        while (sc.hasNext()) {
            try {
                String service = sc.next();
                out.writeUTF(service);
            } catch (Exception e) {
                // TODO: handle exception
                if (mysocket != null) {
                    try {
                        mysocket.close();
                    } catch (IOException ioException) {
                        ioException.printStackTrace();
                    }
                }
                if (in != null) {
                    try {
                        in.close();
                    } catch (IOException ioException) {
                        ioException.printStackTrace();
                    }
                }
                if (out != null) {
                    try {
                        out.close();
                    } catch (IOException ioException) {
                        ioException.printStackTrace();
                    }
                }
                executor.shutdown();
            }
        }
    }
}

for (i = minPort+serial; i < maxPort; i+= threadNum) { Scanner.Result1.append("主机:" + Scanner.hostName.getText()+ " TCP端口:" + i + "\n"); try { hostAddress =InetAddress.getByName(Scanner.hostName.getText()); Socket socket=new Socket(); Scanner.Scanning.setText("正在扫描" + i + "端口"); // 根据主机名和端口号创建套接字地址。 SocketAddress sockaddr = new InetSocketAddress(hostAddress, i); socket.connect(sockaddr, time);// 将此套接字连接到具有指定超时值的服务器。 Scanner.Result2.append("主机:" + Scanner.hostName.getText()+ " TCP:" + i + "- - - - 端口已开放" + "\n"); socket.close(); str += "主机:" + Scanner.hostName.getText()+ " TCP:" + i +"端口已开放" + "\r\n"; }catch (ConnectException e) { Scanner.Result2.append("主机:" + Scanner.hostName.getText()+ " TCP:" + i + " 端口关闭" + "\n"); str += "主机:" + Scanner.hostName.getText()+ " TCP:" + i+"端口关闭" + "\r\n"; } catch (SocketTimeoutException e) { Scanner.Result2.append("主机:" + Scanner.hostName.getText()+ " TCP:" + i + "请求超时" + "\n"); str += "主机:" + Scanner.hostName.getText()+ " TCP:" + i +"请求超时" + "\r\n"; } catch (IOException e) { e.printStackTrace(); } }

这段代码是一个TCP端口扫描器，它会在指定的主机名称和端口范围内进行扫描，并输出扫描结果。为了提高扫描效率，代码使用了多线程，其中的for循环根据线程数量和端口范围计算每个线程需要扫描的端口。在扫描过程中，代码会尝试连接每个指定的TCP端口，如果连接成功则说明端口开放，否则说明端口关闭。如果连接超时或者出现其他异常，则会输出相应的错误信息。最终，代码会将扫描结果输出到Scanner.Result1和Scanner.Result2中，并将结果保存到字符串变量str中。