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About Ilias Tsagklis

Ilias Tsagklis
Ilias is a software developer turned online entrepreneur. He is co-founder and Executive Editor at Java Code Geeks.

Checked and Unchecked Exceptions example

In this example we shall show you how to use a checked and an unchecked exception. A checked exception is anything that is a subclass of Exception, except for RuntimeException and its subclasses. In order to use a checked and an unchecked exception we have followed the steps below:

  • We have created a method, void checkSize(String fileName) that creates a new File with a given String filename and throws an IOException if the filename length is too large.
  • We also create another method, int divide(int x, int y) that divides two int variables and returns the result.
  • When using the two methods, the first one must be put in a try-catch block, whereas the second one can be used without being surrounded by the try-catch block. It is an unchecked exception, so it doesn’t require you to catch it.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.basics;

import java.io.File;
import java.io.IOException;


public class CheckedUncheckedExceptions {

    public static void main(String[] args) {


  // We must catch the checked exception - to test use an existing file!

  try {

  	CheckedUncheckedExceptions.checkSize("testFile.txt");

  } catch (IOException e) {


e.printStackTrace();

  }


  // The unchecked exception doesn't requires you to catch it

  CheckedUncheckedExceptions.divide(1, 0);
    }

    /**
     * This method throws a Checked Exception, so it must declare the
     * Exception in its method declaration
     *
     * @param fileName given file name
     * @throws IOException when the file size is to large.
     */

    public static void checkSize(String fileName) throws IOException {

  File file = new File(fileName);

  if (file.length() > Integer.MAX_VALUE) {


throw new IOException("File size is too large!");

  }
    }

    /**
     * This method throws a RuntimeException.
     * There is no need to declare the Exception in the method declaration
     *
     * @param x the dividend
     * @param y the divisor
     * 
     * @return the division result
     * @throws ArithmeticException when arithmetic exception occurs (divided by zero)
     */
    public static int divide(int x, int y) {

  return x / y;
    }

}

 
This was an example of how to use a checked and an unchecked exception in Java.

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