How to Read a File using Applet?

In this article, we will learn how to read the content of the file using Java and display those contents using Applet.

Approach Used

The user should type the name of the file in the input field that asks for the filename in the output applet window. If the file is already present, it will display the content of the file in the output window. Otherwise, it will display that the file is not found by catching the FileNotFoundException handling.

Program to read a file using Applet

Below is the implementation of the above method:

Java

// Java Program to Read
// A file using Applet
import java.awt.*;
import java.applet.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

// Driver Class
public class FileReaderApplet extends Applet {
    StringBuilder filecontent = new StringBuilder();

    public void init() {
        // Create a text field for user input
        TextField fileNameField = new TextField(20);
        // Create a button to load file
        Button loadButton = new Button("Read File");
        loadButton.addActionListener(e -> {
            String fileName = fileNameField.getText();
            readFileAndDisplay(fileName);
        });

        add(fileNameField);
        add(loadButton);
    }

    public void paint(Graphics g) {
        // String array to store line by line
        String[] lines = filecontent.toString().split("\n");
        // Starting vertical position of text field (display field)
        int y = 40;

        // Display all the lines
        for (String line : lines) {
            // Display line
            g.drawString(line, 20, y);
            // Increase the vertical position for the next line
            y += 20;
        }
    }

    private void readFileAndDisplay(String fileName) {
        try {
            // Create a File object with fileName
            File file = new File(fileName);

            // Create a Scanner to read the file
            Scanner scanner = new Scanner(file);

            // Clear previous content
            filecontent.setLength(0);

            // Read and concatenate all lines into a StringBuilder with "/n" to identify line break
            while (scanner.hasNextLine()) {
                String line = scanner.nextLine();
                filecontent.append(line).append("\n");
            }

            // Close the scanner
            scanner.close();

            // Repaint the applet to display the content in new lines
            repaint();
        } catch (FileNotFoundException e) {
            System.err.println("File not found: " + fileName);
            e.printStackTrace();
        }
    }
}

/*
<applet code="FileReaderApplet" height="300" width="500">
</applet>
*/

Executing the Program

Text File

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Output

Note: Save the file with .txt extension. Make sure that the text file is in the same folder where you saved the program.