帮我用java代码写一个基于jdk8的多线程和swing图形开发一个多线程下载工具

好的，我可以给你提供一个基本的 Java 多线程下载工具的示例代码，使用了 JDK8 的 lambda 表达式和 Swing 图形界面。

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.*;
import java.net.URL;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class MultiThreadDownloader extends JFrame {

    private JPanel panel;
    private JLabel label1, label2, label3;
    private JTextField textField;
    private JButton downloadButton;
    private JProgressBar progressBar;
    private ExecutorService executorService;

    public MultiThreadDownloader() {
        setTitle("Multi-Thread Downloader");
        setSize(500, 200);
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        panel = new JPanel();
        panel.setLayout(new GridLayout(3, 2));

        label1 = new JLabel("URL:");
        textField = new JTextField();
        downloadButton = new JButton("Download");
        downloadButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                startDownload();
            }
        });

        label2 = new JLabel("Status:");
        label3 = new JLabel("Ready");

        progressBar = new JProgressBar();
        progressBar.setStringPainted(true);

        panel.add(label1);
        panel.add(textField);
        panel.add(label2);
        panel.add(label3);
        panel.add(downloadButton);
        panel.add(progressBar);

        getContentPane().add(panel, BorderLayout.CENTER);

        executorService = Executors.newFixedThreadPool(5); // 创建一个固定大小的线程池
    }

    private void startDownload() {
        String urlStr = textField.getText();
        if (urlStr.isEmpty()) {
            JOptionPane.showMessageDialog(this, "Please enter a URL.");
            return;
        }

        try {
            URL url = new URL(urlStr);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            int responseCode = conn.getResponseCode();
            if (responseCode != 200) {
                JOptionPane.showMessageDialog(this, "Failed to connect to the server.");
                return;
            }

            int contentLength = conn.getContentLength();
            if (contentLength <= 0) {
                JOptionPane.showMessageDialog(this, "No file to download.");
                return;
            }

            progressBar.setMinimum(0);
            progressBar.setMaximum(contentLength);
            progressBar.setValue(0);

            String fileName = getFileName(conn);
            label3.setText("Downloading " + fileName);
            downloadButton.setEnabled(false);

            executorService.execute(() -> {
                try (InputStream inputStream = url.openStream();
                     FileOutputStream outputStream = new FileOutputStream(fileName)) {
                    byte[] buffer = new byte[4096];
                    int bytesRead;
                    int downloadedSize = 0;
                    while ((bytesRead = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, bytesRead);
                        downloadedSize += bytesRead;
                        progressBar.setValue(downloadedSize);
                    }
                    label3.setText("Download completed.");
                    downloadButton.setEnabled(true);
                } catch (IOException e) {
                    e.printStackTrace();
                    label3.setText("Download failed.");
                    downloadButton.setEnabled(true);
                }
            });

        } catch (IOException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(this, "Invalid URL.");
        }
    }

    private String getFileName(HttpURLConnection conn) {
        String fileName = conn.getURL().getFile();
        int index = fileName.lastIndexOf('/');
        if (index > 0) {
            fileName = fileName.substring(index + 1);
        }
        return fileName;
    }

    public static void main(String[] args) {
        MultiThreadDownloader downloader = new MultiThreadDownloader();
        downloader.setVisible(true);
    }
}

这个示例代码实现了一个简单的多线程下载工具，它支持从指定的 URL 下载文件，并使用 Swing 图形界面展示下载进度和状态。在下载文件时，它使用了多线程来提高下载速度。你可以根据自己的需求进行修改和扩展。