Java Exception Handling

The normal flow of a program disrupts when an exception occurs. This stops the Java program and an error message generates. Consider, Exception as an abnormal condition, which needs to be handled, and Exception Handling as a mechanism used to handle it. This includes handling runtime errors like ClassNotFoundException, IOException, RemoteException, etc.

The following errors can occur while running a Java program:

  • Wrong Data as Input
  • Opening a File that does not exist at the same location

Code without Exception Handling

Before moving further, let us run a Java code without handling the exceptions.


The output displays an error but we are not handling it using try…catch:

Now, we will see how to handle the above code with Exception Handling in Java.

Exception Handling in Java

To handle Exceptions, the following concepts are defined in Java:

  • try catch in Java
  • finally in Java
  • throw in Java

Let us learn about them one by one with examples:

try catch in Java

To catch exceptions in Java, use the try…catch pair. The code goes inside both try catch, and is called the protected code. The try block cannot be used alone and is followed by either catch statement or a finally block. Let us see the syntax:

Handle Exceptions with try catch

Let us now see an example to handle exceptions in Java with try…catch:


Handle Exceptions with try catch and display the exception

We can also display the exception. Here’s an example:


The above displays the exact error i.e., the elements are 4, but the value is searched for index 5.

Multiple catch blocks in Java

After a try block, we can add more than one catch block. The exception is thrown to the 1st catch block.

Let us see the syntax of the catch block in Java:

Only one catch block executes since only a single exception occurs at a time. The multiple catch blocks should be ordered accordingly. The catch for ArithmeticException, ArrayIndexOutOfBoundsException, etc. should come before Exception.

Let us see an example. Here, we have set the ArithmeticException and ArrayIndexOutOfBoundsException, but since the error is related to an array out of bound, therefore the catch which gets executed is ArrayIndexOutOfBoundsException:


finally in Java

The finally in Java executes a code after try catch. Whether the exception is handled or not, the statements in the finally executes. Therefore, add any key code or statement you want to display irrespective of the result inside the finally block. Let us see the syntax of the finally block in Java:

Let us see an example of finally in Java:


throw keyword in Java

To throw an exception, the throw keyword is used. It throws an exception explicitly. The throw keyword is followed by an exception type, like ArithmeticException, ArrayIndexOutOfBoundsException, SecurityException, etc.

Let us see an example wherein we will throw and error if a student gets less than 50 marks and failed the exam:


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Java File Handling
Java - User Input
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