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5.6 BASIC CONCEPT OF AN EXCEPTION
During the execution of a program, an error may occur, which may stop the execution of the program. This error is
known as an exception.
A message is generated, which sometimes becomes difficult for the users to understand. In Java, a programmer can
modify the messages so that they may be easily understood.

5.6.1 Types of Exception
There are two types of exceptions in Java, which are as follows:
• Checked exceptions
• Unchecked exceptions

Checked Exceptions
Except for runtime exceptions, all exceptions are known as checked exceptions as they are checked by the compiler.
For example, IOException, ClassNotFoundException, etc.

Unchecked Exceptions
Exceptions that bypass the compiler are known as unchecked exceptions. They are also known as runtime exceptions.
For example, NullPointerException, ArithmeticException, etc.

5.6.2 Exception Handling
When an exception occurs, the program stops immediately with a system-generated message. To provide a
user-friendly message, we need to handle the thrown exceptions. Using Exception Handling, we can ensure that the
flow of the program doesn’t break when an exception occurs. So, exception handling is a mechanism to handle errors
that occur during the execution of the program so that the normal flow of the code can be maintained.

Java try-catch block
The “try” block and “catch” block help to handle the exception raised. In the “try” block, we write the codes that are
needed to test for the errors and the “catch” block is used to define those blocks that are going to be executed if any
error occurs in the “try” block.
Syntax of try-catch block:
try {
// Block of code to try
}
catch(Exception e) {
// Block of code to handle errors
}
Java throw statement
When the throw statement executes, the nearest catch statement is checked to see what type of exception has been thrown.
Syntax of throw statement:

throw ThrowableInstance;
Java throws keyword
A method can throw many types of exceptions during the execution of the program. The throws keyword declares all
these types of exceptions. This is used to help the programmers with prior knowledge about what types of exceptions
are to be handled.
Syntax of throws keyword:

return_type name_of_method(list_of_parameters) throws exception_list
{

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