java throw keyword /Chapter 9 /Exception Handling

java throw keyword:-

throw keyword used to create our own exception object explicitly and we can handover this (our own created) exception object to JVM manually.

example:-

The main objective of throw keyword is to hand over our created exception object to JVM manually.

Let's take two example where the output will be same.

Example 1:-

class Test
{
    public static void main(String[] args)
    {
       System.out.println(10/0);
    }
}

Output is:-



In the above program main() method is responsible for creating the exception object and handing over to JVM.

Example 2:-

class Test 
{
	public static void main(String[] args) 
	{
		throw new ArithmeticException("/ by zero");
	}
}

Output is:-



In the above case, the programmer is responsible for creating the exception object and handing over to JVM manually.

Note: throw keyword is the best choice for user defined exceptions or customized exceptions.

Important LoopHole:-

1. After the throw statement, we are not allowed to write any statement directly otherwise, we will get Compile time error saying"Unreachable statement."

example 3:-

class Test 
{
	public static void main(String[] args) 
	{
		throw new ArithmeticException("/ by zero");
                System.out.println("javabychetan");
	}
}

Compile Time Error

2. We can use throw keyword only for Throwable types (which extends Throwable class ) only. If we are trying for normal java objects then we will get compile time error saying"incompatible types".

example 4.

class Test 
{
	public static void main(String[] args) 
	{
		throw new Test();
	}
}

Compile Time Error