java弹出窗放textarea_怎么让文件的内容在textArea中显示出来？

可以使用以下代码实现在Java Swing中弹出窗口并在TextArea中显示文件内容的功能：

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class FileViewer extends JFrame implements ActionListener {

    private JButton openButton;
    private JTextArea textArea;

    public FileViewer() {
        super("File Viewer");

        // Create components
        openButton = new JButton("Open");
        openButton.addActionListener(this);

        textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane(textArea);

        // Add components to content pane
        Container contentPane = getContentPane();
        contentPane.add(openButton, BorderLayout.NORTH);
        contentPane.add(scrollPane, BorderLayout.CENTER);

        // Set window properties
        setSize(400, 300);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
        // Create and show window
        FileViewer fileViewer = new FileViewer();
        fileViewer.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == openButton) {
            // Create file chooser dialog
            JFileChooser fileChooser = new JFileChooser();
            int result = fileChooser.showOpenDialog(this);

            if (result == JFileChooser.APPROVE_OPTION) {
                // Get selected file
                File file = fileChooser.getSelectedFile();

                try {
                    // Read file contents
                    BufferedReader reader = new BufferedReader(new FileReader(file));
                    String line;
                    StringBuilder sb = new StringBuilder();
                    while ((line = reader.readLine()) != null) {
                        sb.append(line);
                        sb.append(System.lineSeparator());
                    }
                    reader.close();

                    // Set text area contents
                    textArea.setText(sb.toString());
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        }
    }
}

这段代码会创建一个名为 "File Viewer" 的窗口，其中包含一个 "Open" 按钮和一个文本区域。当用户点击 "Open" 按钮时，会弹出一个文件选择器对话框，用户可以选择要读取的文件。然后，程序会读取文件内容并将其显示在文本区域中。