Java FileInputStream Class

FileInputStream class in Java is useful for reading data from a file in the form of a Java sequence of bytes. FileInputStream is meant for reading streams of raw bytes such as image data. For reading streams of characters, consider using FileReader.

Example: FileInputStream class to read data from file.

import java.io.*;

public class Geeks {

    public static void main(String[] args)
    {

        // Use try-with-resources to handle resource
        // management
        try (FileInputStream fi
             = new FileInputStream("file1.txt")) {

            // Illustrating getChannel() method
            System.out.println("Channel: "
                               + fi.getChannel());

            // Illustrating getFD() method
            System.out.println("File Descriptor: "
                               + fi.getFD());

            // Illustrating available method
            System.out.println("Number of remaining bytes: "
                               + fi.available());

            // Illustrating skip() method
            fi.skip(4);

            System.out.println("File Contents:");

            // Reading characters from FileInputStream
            int ch;
            while ((ch = fi.read()) != -1) {
                System.out.print((char)ch);
            }
        }
        catch (FileNotFoundException e) {
            System.out.println(
                "File not found: Ensure 'file1.txt' exists in the working directory.");
        }
        catch (IOException e) {
            System.out.println(
                "An error occurred while reading the file: "
                + e.getMessage());
        }
    }
}

Output: 

Declaration

Class declaration of FileInputStream is given below:

public class FileInputStream extends InputStream

Note: FileInputStream is a subclass of InputStream, which is used for reading bytes from a file.

Constructors of FileInputStream Class

1. FileInputStream(String name)

Creates an input file stream to read from a file with the specified name. 

Example:

FileInputStream fi = new FileInputStream(“example.txt”);

2. FileInputStream(File file)

Creates an input file stream to read from the specified File object. 

Example:

File f = new File(“example.txt”);

FileInputStream fi = new FileInputStream(f);

3. FileInputStream(FileDescriptor fdobj)

Creates an input file stream to read from the specified file descriptor. 

Example:

FileDescriptor fd = FileDescriptor.in;

FileInputStream fi = new FileInputStream(fd); 

Methods of Java FileInputStream Class

Steps to Read Data using FileInputStream

Following steps are typically followed to read data from the file.

Step 1: Attach a file to a FileInputStream

This step will enable us to read data from the file as shown below as follows

FileInputStream fi =new FileInputStream(“file.txt”);

Step 2: Use read() method to read data

Use the read() method of FileInputStream to read bytes of data from the file.

int ch = fileInputStream.read();

Step 3-A: Check for End of File

When there is no more data available to read further, the read() method returns -1; 

Step 3-B: Print the Data

Convert the integer value returned by read() into character (using(char)) and then print it.

System.out.print((char) ch);

Example: Read Data from a File Using FileInputStream

Here’s an implementation of the steps discussed above to read the contents of a file and display it.

Note: To ensure the program runs correctly, create a file named file.txt in the working directory. Once the working directory is determined, create the file file.txt in that location. Add the following content to the file:

this is my first code

this is my second code

Save the file and run the program. The program will read and display the contents of file.txt as output.

Example:

// Java Program to Demonstrate the working of
// FileInputStream Class
import java.io.*;

public class Geeks {

    public static void main(String args[])
    {
        try {
          
            // Attach a file to FileInputStream
            FileInputStream fi
                = new FileInputStream("file.txt");

            // Read data from FileInputStream
            int ch;
            while ((ch = fi.read()) != -1) {
              
                // Print the data
                System.out.print((char)ch);
            }

            // Close the stream
            fi.close();
        }
        catch (FileNotFoundException e) {
            System.out.println(
                "File not found: Ensure the file exists.");
        }
        catch (IOException e) {
            System.out.println(
                "An error occurred while reading the file.");
        }
    }
}

Output: 

Key Features of FileInputStream

• Byte Oriented Stream: It reads data in the form of bytes
• Direct Access: It directly reads the file content from the disk without buffering
• Platform Independent: It can work on any operating system

N

Nishant Sharma

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Article Tags :

• Java

Practice Tags :

• Java