How to read data from a file using FileInputStream?

The FileInputStream class reads the data from a specific file (byte by byte). It is usually used to read the contents of a file with raw bytes, such as images.

To read the contents of a file using this class −

• First of all, you need to instantiate this class by passing a String variable or a File object, representing the path of the file to be read.

FileInputStream inputStream = new FileInputStream("file_path"); or, File file = new File("file_path"); FileInputStream inputStream = new FileInputStream(file);

• Then read the contents of the specified file using either of the variants of read() method −

  • int read() − This simply reads data from the current InputStream and returns the read data byte by byte (in integer format).

    This method returns -1 if the end of the file is reached.

  • int read(byte[] b) − This method accepts a byte array as parameter and reads the contents of the current InputStream, to the given array.

    This method returns an integer representing the total number of bytes or, -1 if the end of the file is reached.

  • int read(byte[] b, int off, int len) − This method accepts a byte array, its offset (int) and, its length (int) as parameters and reads the contents of the current InputStream, to the given array.
  • This method returns an integer representing the total number of bytes or, -1 if the end of the file is reached.

Example

Assume we have the following image in the directory D:/images

Following program reads contents of the above image using the FileInputStream.

Example

import java.io.File; import java.io.FileInputStream; import java.io.IOException; public class FileInputStreamExample {    public static void main(String args[]) throws IOException {       //Creating a File object       File file = new File("D:/images/javafx.jpg");       //Creating a FileInputStream object       FileInputStream inputStream = new FileInputStream(file);       //Creating a byte array       byte bytes[] = new byte[(int) file.length()];       //Reading data into the byte array       int numOfBytes = inputStream.read(bytes);       System.out.println("Data copied successfully...");    } }

Output

Data copied successfully...