Close Input Stream and Release System Resources in Java

This Java article discusses the InputStream.close() function to close the input stream and free up system resources. The method java.io.InputStream.close() is used to close this input stream and release any system resources associated with the stream. This method requires no parameters and returns no value. Also, the IOException is thrown when an I/O error occurs.

Problem Statement

Given an input stream, write a Java program to close this input stream and release any system resources associated with it. Ensure that the program handles any exceptions that may occur if the stream is already closed or an I/O error is encountered.
Input

An input stream that reads a file located at C://JavaProgram//data.txt.

Output

The number of bytes are: 4
Error!!! The input stream is closed

Steps to close the input stream and release system resources

The following are the steps to close the input stream and release system resources

• Import the necessary classes from the java.io package (FileInputStream and InputStream).
  
• Create an InputStream object and use the FileInputStream to read a file.
  
• Retrieve the available bytes using the available() method to check the current status of the stream.
  
• Close the input stream using the close() method to release resources.
  
• Attempt to access the input stream again after closing it, and handle any exceptions that occur, such as an IOException.

Java program to close an InputStream and release resources

The following is an example of closing an InputStream and releasing resources

import java.io.FileInputStream;
import java.io.InputStream;
public class Demo {
   public static void main(String[] args) throws Exception {
      InputStream i = null;
      int num = 0;
      try {
         i = new FileInputStream("C://JavaProgram//data.txt");
         num = i.available();
         System.out.println("The number of bytes are: " + num);
         i.close();
         num = i.available();
         System.out.println("The number of bytes are: " + num);
      } catch(Exception e) {
         System.out.print("Error!!! The input stream is closed");
      }
   }
}

Output

The number of bytes are: 4
Error!!! The input stream is closed

Code Explanation

Using the FileInputStream class, an input stream is created, the number of bytes that can be read is checked with available() and the output is shown. When a stream is closed using close(), and there is an attempt to read the stream, an exception occurs since the stream is already closed. The exception is handled and a message "Error!!! The input stream is closed" is shown as a part of the error handling.