Java InputStream Class

In this tutorial, we will learn about the Java InputStream class and its methods through an example.

The InputStream class in the java.io package is an abstract superclass that represents a byte input stream.

Since InputStream is an abstract class, it is not used by itself. However, its subclasses can be used to read data.

InputStream subclasses

To use the InputStream functionality, we can use its subclasses. Its subclasses include:

• FileInputStream

• ByteArrayInputStream

• ObjectInputStream

In the next tutorial, we will learn all these subclasses.

Create an InputStream

To create an InputStream, we must first import the java.io.InputStream package. After importing the package, we can create the input stream.

//　Create an InputStream
InputStream object1　= new FileInputStream();

Here, we use FileInputStream to create an input stream. This is because InputStream is an abstract class. Therefore, we cannot create an InputStream object.

Note: We can also create input streams from other subclasses of InputStream.

InputStream methods

The InputStream class provides different methods implemented by its subclasses. Here are some commonly used methods

• read() - Read a byte of data from the input stream

• read(byte[] array) - Read bytes from the stream and store them in the specified array

• available() - Return the number of available bytes in the input stream

• mark() - Mark the position of the data in the input stream

• reset() -Return the control point to the point set by mark in the stream

• markSupported()- Check if the stream supports mark() and reset() methods

• skips() - Skip and discard the specified number of bytes in the input stream

• close() - Close Input Stream

Example: InputStream using FileInputStream

The following is the implementation of the InputStream method using FileInputStream class.

Assuming we have a file namedinput.txtwhich contains the following content.

This is a line of text in the file.

Let's try to use FileInputStream (a subclass of InputStream) to read this file.

import java.io.FileInputStream;
import java.io.InputStream;
public class Main {
　　　　public static void main(String args[]) {
　　　　　　　　byte[] array = new byte[100];
　　　　　　　　try {
　　　　　　　　　　　　InputStream input = new FileInputStream("input.txt");
　　　　　　　　　　　　System.out.println("Available bytes in the file:");　+　input.available());
　　　　　　　　　　　　//Read bytes from the input stream
　　　　　　　　　　　　input.read(array);
　　　　　　　　　　　　System.out.println("Read data from file:");
　　　　　　　　　　　　//Convert byte array to string
　　　　　　　　　　　　String data = new String(array);
　　　　　　　　　　　　System.out.println(data);
　　　　　　　　　　　　//Close Input Stream
　　　　　　　　　　　　input.close();
　　　　　　　　}
　　　　　　　　catch (Exception e) {
　　　　　　　　　　　　e.getStackTrace();
　　　　　　　　}
　　　　}
}

Output Result

Available bytes in file:　35
Data read from file:
This is a line of text in the file.

In the above example, we created an input stream using the FileInputStream class. The input stream is associated with a fileinput.txtLink.

InputStream input = new FileInputStream("input.txt");

To read frominput.txtWe have implemented these two methods to read data from a file.

input.read(array);　　　　　　//Read Data from Input Stream
input.close();　　　　　　　　　　　　　//Close Input Stream