java method throws code example

Example 1: importance of throws keyword in java

Throws statement is used at the end of method signature to indicate that 
an exception of a given type may be thrown from the method.
The main purpose of throws keyword is to delegate responsibility of 
exception handling to the caller methods, in the case of checked exception.
In the case of unchecked exceptions, it is not required to use throws keyword.
We can use throws keyword only for throwable types otherwise compile time error 
saying incompatible types.
An error is unchecked, it is not required to handle by try catch or by throws.
  
  Syntax : Class Test{
Public static void main(String args[]) throws IE{
}}

The method should throw only checked exceptions and subclasses 
of checked exceptions. It is not recommended to specify exception 
superclasses in the throws class when the actual exceptions thrown in 
the method are instances of their subclass.

Example 2: throw keyword in java

Generally JVM throws the exception and we handle the exceptions by 
using try catch block. But there are situations where we have to throw 
userdefined exceptions or runtime exceptions. In such case we use throw keyword 
to throw exception explicitly.

  Syntax : throw throwableInstance;

Throwable instance must be of type throwable or any of its subclasses.
After the throw statement execution stops and subsequent statements are not 
executed. Once exception object is thrown JVM checks is there any catch 
block to handle the exception. If not then the next catch statement till it 
finds the appropriate handler. If appropriate handler is not found, 
then default exception handler halts the program and prints the description 
and location of exception. In general we use throw keyword for throwing 
userdefined or customized exception.