File handling

Introduction to File Handling

File handling is a crucial aspect of programming as it allows data to be saved and accessed in files. It enables a program to store data permanently, which can then be used by the program in future executions.

Reading and Writing Files:

In Java, we can use the File class to represent a file and the FileWriter and FileReader classes to read and write files. The following code snippet demonstrates how to write data to a file using FileWriter:

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterDemo {
    public static void main(String[] args) {
        try {
            FileWriter writer = new FileWriter("output.txt");
            writer.write("Hello, World!");
            writer.close();
            System.out.println("Data written to file.");
        } catch (IOException e) {
            System.out.println("An error occurred.");
            e.printStackTrace();
        }
    }
}

Working with Text Files and Binary Files:

Java provides different classes to handle text files and binary files. The FileWriter and FileReader classes are used to read and write text files, while the ObjectOutputStream and ObjectInputStream classes are used to read and write binary files. The following code snippet demonstrates how to write an object to a binary file using ObjectOutputStream:

import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;

public class ObjectOutputStreamDemo {
    public static void main(String[] args) {
        try {
            FileOutputStream fos = new FileOutputStream("data.dat");
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            Person person = new Person("John", 25);
            oos.writeObject(person);
            oos.close();
            fos.close();
            System.out.println("Object written to file.");
        } catch (IOException e) {
            System.out.println("An error occurred.");
            e.printStackTrace();
        }
    }
}

Error Handling:

When working with files, it is important to handle errors that may occur. This can be achieved using try-catch blocks. The following code snippet demonstrates how to read data from a file using FileReader and handle any errors that may occur:

import java.io.FileReader;
import java.io.IOException;

public class FileReaderDemo {
    public static void main(String[] args) {
        try {
            FileReader reader = new FileReader("input.txt");
            int data = reader.read();
            while (data != -1) {
                System.out.print((char) data);
                data = reader.read();
            }
            reader.close();
        } catch (IOException e) {
            System.out.println("An error occurred.");
            e.printStackTrace();
        }
    }
}

In the above code snippet, we are reading data from a file using FileReader and displaying it to the console. The read() method of FileReader returns -1 if the end of the file is reached.

Overall, file handling is an important aspect of programming and is useful in a variety of applications, from storing user preferences to saving game progress.