Nikos Maravitsas

About Nikos Maravitsas

Nikos has graduated from the Department of Informatics and Telecommunications of The National and Kapodistrian University of Athens. Currently, his main interests are system’s security, parallel systems, artificial intelligence, operating systems, system programming, telecommunications, web applications, human – machine interaction and mobile development.

java.io.IOException – How to solve IOException

In this example we are going to talk about a very common exception that many java developers stumble upon when dealing with IO operations in their program : IOException. This exception occurs when an IO operation has failed for some reason. It is also a checked exception which means that your program has to handle it. All bult-in Java IO methods that might cause an IOException, explicitly throw it so that your program can handle it. It is also worth noting that the IOException object that your program receives is accompanied by a String message that can inform you as accurately as possible for the cause of the exception.

Also, IOException is the most general class that can describe an IOException. Several subclass of it exist in order to reveal the problem that occurred in a more specific and detailed manner. Some of the most well know sub classes are FileNotFoundException, EOFException, UnsupportedEncodingException, SocketException, SSLException

1. A simple case of IOException

Let’s see a very simple case of an IOException. In the following example we are going to try to read some lines of text form a file that does not exist:

IOExceptionExample.java:

package com.javacodegeeks.core.io.ioexception;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class IOExceptionExample {

	private static String filepath = "C:\\Users\\nikos\\Desktop\\TestFiles\\testFile2.txt";
	
	public static void main(String[] args) {
		
		BufferedReader br = null;
		String curline;
		try {
			br = new BufferedReader(new FileReader(filepath));

			while ((curline = br.readLine()) != null) {
				System.out.println(curline);
			}

		} catch (IOException e) {
		
			System.err.println("An IOException was caught :"+e.getMessage());
		
		}finally{
			
			try {
				
				if(br != null)
					br.close();
			
			} catch (IOException e) {
				
				e.printStackTrace();
			}
		}

	}

}

Now, when I run this program, because the file C:\\Users\\nikos\\Desktop\\TestFiles\\testFile2.txt does not exist, it will output:

An IOException was caught :C:\Users\nikos\Desktop\TestFiles\testFile2.txt (The system cannot find the file specified)

As you can see the message is pretty informative of the cause of the problem. Note that when the file you are trying to access does not exist, a more “specialized” exception is thrown, FileNotFoundException.

2. How to solve IOException

As you’ve seen IOException is a very general exception that occurs when an IO operations fails. So you can understand that there is no standard way on how to solve this exception. The best thing you can do is to explicitly handle the exception in a try-catch block and print out the message of the exception. Then you can take the correct actions to solve this situation. For example, in the previous code snippet, the message clearly states that the file does not exist. So you should go ahead and create the file. It can also say :”Permission Denied”. This means that you should check if you have the permission to perform the action you requested in that file. If you are working with streams and especially with sockets and the stream is closed in the middle of your session you could see a message like :”Stream Closed” that designates the problem exactly .

Download Source Code

This was an example on java.io.IOException. Download the source code of this example here : IOExceptionExample.zip

Related Whitepaper:

Java Essential Training

Author David Gassner explores Java SE (Standard Edition), the language used to build mobile apps for Android devices, enterprise server applications, and more!

The course demonstrates how to install both Java and the Eclipse IDE and dives into the particulars of programming. The course also explains the fundamentals of Java, from creating simple variables, assigning values, and declaring methods to working with strings, arrays, and subclasses; reading and writing to text files; and implementing object oriented programming concepts. Exercise files are included with the course.

Get it Now!  

Examples Java Code Geeks and all content copyright © 2010-2014, Exelixis Media Ltd | Terms of Use | Privacy Policy
All trademarks and registered trademarks appearing on Examples Java Code Geeks are the property of their respective owners.
Java is a trademark or registered trademark of Oracle Corporation in the United States and other countries.
Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation.
Do you want to know how to develop your skillset and become a ...
Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you two of our best selling eBooks for FREE!

Get ready to Rock!
You can download the complementary eBooks using the links below:
Close