JavaFileInputStream

FileInputStream

So far, you have used theScanner class toread text files.Scanner is very convenient for text because it can split input into lines, words, or numbers. However, sometimes you need more control. For example, when readingbinary data (like images, audio, or PDFs), or when you need full control of raw bytes. In those cases, you useFileInputStream.

Read a Text File (Basic Example)

This example usesFileInputStream to read a text file, one byte at a time, and print the result as characters:

import java.io.FileInputStream;  // Import FileInputStreamimport java.io.IOException;      // Import IOExceptionpublic class Main {  public static void main(String[] args) {    // try-with-resources: FileInputStream will be closed automatically    try (FileInputStream input = new FileInputStream("filename.txt")) {      int i;  // variable to store each byte that is read      // Read one byte at a time until end of file (-1 means "no more data")      while ((i = input.read()) != -1) {        // Convert the byte to a character and print it to the console        System.out.print((char) i);      }    } catch (IOException e) {      // If an error happens (e.g. file not found), print an error message      System.out.println("Error reading file.");    }  }}

Explanation: This program opensfilename.txt, reads it byte by byte, and prints the result as characters in the console.

Copy a Binary File (Real-World Example)

The real strength ofFileInputStream is that it can handleany file type, not just text. Here is an example that copies an image file:

import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;public class CopyFile {  public static void main(String[] args) {    // Copy image.jpg into copy.jpg    try (FileInputStream input = new FileInputStream("image.jpg");         FileOutputStream output = new FileOutputStream("copy.jpg")) {      int i;      while ((i = input.read()) != -1) {        output.write(i);  // write the raw byte to the new file      }      System.out.println("File copied successfully.");    } catch (IOException e) {      System.out.println("Error handling file.");    }  }}

Explanation: This program readsimage.jpg and writes it intocopy.jpg. Since it works with raw bytes, it can copyany kind of file - text, images, audio, or PDFs.

Note: The program also usesFileOutputStream. WhileFileInputStream is used toread bytes from a file,FileOutputStream is used towrite bytes to a file. Together, they make it possible to copy any kind of file.

You will learn more aboutFileOutputStream in the next chapter.

Choosing the Right Class

Java gives you several ways to read files. Here's when to pick each one:

• Scanner - best forsimple text and when you want to parse numbers or words easily.
• BufferedReader - best forlarge text files, because it is faster and reads line by line.
• FileInputStream - best forbinary data (images, audio, PDFs) or when you need full control of raw bytes.