(Retrieve files from Web) Write a Java program that retrieves a file from a Web server, as shown in Figure 17.32. The user interface includes a text field in which to enter the URL of the file name, a text area in which to show the file, and a button that can be used to submit an action. A label is added at the bottom of the applet to indicate t…

URLTest.java

import java.awt.*;
import java.awt.event.*;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Scanner;
import javax.swing.*;

public class URLTest extends JFrame {
    
    JTextField field = new JTextField(40);
    JButton view = new JButton("View");
    JTextArea area = new JTextArea(10, 0);
    JLabel label = new JLabel("");
    
    URLTest() {
        JScrollPane scroll = new JScrollPane(area);
        JPanel p1 = new JPanel(new BorderLayout());
        p1.add(new JLabel("File name"), BorderLayout.WEST);
        p1.add(field);
        p1.add(view, BorderLayout.EAST);
        
        JPanel p2 = new JPanel(new BorderLayout());
        p2.add(scroll);
        label.setHorizontalAlignment(JLabel.LEFT);
        p2.add(label, BorderLayout.SOUTH);
        
        add(p1, BorderLayout.NORTH);
        add(p2);
        
        view.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                loadTextFromUrl(field.getText());
            }
        });
    }
    
    private String loadTextFromUrl(String stringUrl) {
        StringBuilder builder = new StringBuilder();
        try {
            URLConnection url = new URL(stringUrl).openConnection();
            url.setConnectTimeout(30000);
            Scanner input = new Scanner(url.getInputStream());
            while (input.hasNext()) {
                builder.append(input.nextLine()).append("\n");
            }
            input.close();
            area.setText(builder.toString());
            label.setText("File loaded successfully");
        } catch (MalformedURLException ex) {
            System.out.println(ex);
            label.setText("File loaded failed");
        } catch (IOException ex) {
            System.out.println(ex);
            label.setText("File loaded failed");
        }
        
        return builder.toString();
    }
    
    public static void main(String[] args) {
        JFrame frame = new URLTest();
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}