Java Program to Perform Read and Write Operations for a File using Applet

This is a Java Program to Perform Read and Write Operations for a File using Applet

Problem Description:

We have to write a program in Java such that it performs the read and write operations for a file using an applet.

Expected Input and Output:

For performing read and write operations, we can have the following different sets of input and output.

1. To Perform Read Operation : When the file is present in the directory.

2. To Perform Read Operation: When the file is not present in the directory.

3. To Perform Write Operation: When the file is present in the directory.

4. To Perform Write Operation: When the file is not present in the directory.

Problem Solution

1. Create a text field to enter the file name.
2. Create two buttons for the read and write operations.
3. Create a text area when the contents of the file is displayed or written.
4. Use the FileReader class to read the file.
5. Use the FileWriter class to write to the file.

Program/Source Code

Here is source code of the Java Program to perform read & write operations. The program is successfully compiled and tested using javac compiler on Fedora 30. The program output is also shown below.

/* Java Program to Perform Read and Write Operations */
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class File extends Applet implements ActionListener
{
    TextField file;
    TextArea text;
    //Initialize the applet
    public void init()
    {
    setBackground(Color.white);
    setLayout(null);


    Label label = new Label("File Name :");
    label.setBounds(100,0,100,40);
    this.add(label);


    file = new TextField();
    file.setBounds(200,0,200,40);
    this.add(file);


    text = new TextArea("",0,0,TextArea.SCROLLBARS_NONE);
    text.setBounds(50,75,400,300);
    this.add(text);


    Button read = new Button("Read From File");
    read.setBounds(75,400,150,25);
    this.add(read);
    read.addActionListener(this);


    Button write = new Button("Write To File");
    write.setBounds(275,400,150,25);
    this.add(write);
    write.addActionListener(this);
    }
    //Function to call functions for operations selected
    public void actionPerformed(ActionEvent e)
    {
    String button = e.getActionCommand();
    if(button.equals("Read From File"))
    {
        read();
    }
    else
    {
        write();
    }
    }
    //Function to Read the File
    public void read()
    {
    try
    {
        FileReader obj = new FileReader(file.getText());
        int i;
        text.setText("");
        while((i=obj.read())!= -1)
        {
        text.setText(text.getText()+(char)i);
        }
        obj.close();
    }
    catch(Exception E)
    {
        text.setText(E.getMessage());		
    }
    }
    //Function to Write to the File
    public void write()
    {
    try
    {
        FileWriter obj = new FileWriter(file.getText());
        obj.write(text.getText());
        obj.close();
        text.setText("File Written Successfully");
    }
    catch(Exception E)
    {
        text.setText(E.getMessage());
    }
    }
}
/*
<applet code = File.class width=500 height=500>
</applet>
*/

>>> javac File.java
>>> appletviewer File.java

Program Explanation

1. To read the file use FileReader class.
2. To write to the file use FileWriter class.

Runtime Test Cases

Here’s the run time test cases for performing read and write for different input cases.

Test case 1 – To Test Write Operation.

Test case 2 – To Test Read Operation When File is Present.

Test case 3 – To Test Read Operation When File is Not Present.