Monday, 12 August 2019

Exception handling in Java - handle exception in java

Exception handling in Java

Exception handling in java

Exception handling is a very important feature in Java. This helps in handling bad user experience. Exceptions are run time errors. Exception is a situation that stops the program while you are running. Just as the amount of memory your program needs to execute, if your memory is not in your computer, then execution of your program will stop. This is the out of memory exception. Similar situations are called exceptions in java and they are handled. Exception handing plays very important part in selenium. Exception handling interview questions will be based on below tutorials. Let's start with exception handing in details

Program Crashes

Just like if you forget to put semicolon in front of a statement while creating a program, then the program error shows you and is not compiled. Similarly, when exception is generated in java (or not handled), your program stops and does not execute.

Handle a java program

If you want that your program does not stop executing on the exception, then for this you have to handle exceptions. This is called exception handling in java. When you handle exceptions, your program does not stop at the exception, but instead executes the rest of the code by skipping the exception code.

Java Exception Handling

In Java, you handle exceptions with the help of some keywords. All these keywords together form a structure that is very easy to implement.


The code of your program that can generate an exception, you write it in the try block. For example, you are doing a mathematical operation in the program and you feel that an exception can be generated, then you write that code in the try block.


Most of the possible exceptions are already defined in the java library for you and these exceptions throw java automatically, you just have to handle them. But if you want, you can also create your own exceptions. You have to throw such exceptions yourself, for this you use throw keyword. You can also throw a predefined exception if you want.


If an exception is generated in the try block, it is handled in this block. You write the code in this block that you want to execute when an exception occurs. For example, you can print a message that tells the user that an exception has been generated.


You can use nested try blocks. And in such a situation, if you want an exception to handle the outer try block, then in such a situation you use the throws keyword. You write the names of all exceptions by putting the throws keyword next to the definition in the method. If an exception occurs, the outer try block handles it.


After handling the exception, you finally write the code you want to execute. After the exception in the try block, the compiler does not execute that code and finally executes the block directly after the catch block.

Steps to Handle Java Exceptions

First of all, write the code in the try block from which exception can be generated.
After the try block, write the code to handle runtime exception in java in the catch block. As such, you can print a message related to the exception.

After handling the exception, finally write the code that you want to execute. It is very important for you to know about exceptions before handling the Exceptions. There are some exceptions that occur regularly in java. You can easily practice on these common exceptions and improve your skill. Some common exceptions coming regularly in Java are being described below.

Exceptions in Java

Arithmetic Exceptions

Any arithmetic error such as Arithmetic Exception is generated if you try to divide a number by zero or try to store more value than its size in a variable.

Class cast exception

Class-Cast-Exception is generated if you want to store the reference of a class to another class and if the first class is not a subclass of the second class.

Array Store Exception

If you have created a string array and you try to store string in it, then Array-Store Exception is generated.

Array Index Out Of Bounds Exception

Array-Index-Out-Of-Bounds-Exception is generated if the size of your array is 10 and you try to store the value at the 11th position or access the 11th position.

Illegal Argument Exception

Illegal-Argument-Exception is generated when you pass an invalid argument in a method such as passing the string instead of int.

Null Pointer Exception

In Java you can assign null value to a reference variable, but if you try to use this reference variable, NullPointerException is generated.

 Number Format Exception

When you try to cast a string value to a number, a Number-Format-Exception occurs.

We will bring more exception handling in java with examples. To know more about testing check this : Manual Testing