What is the use of throws in java?

Answer 1

The throw keyword in java causes a declared exception to be thrown. For example, if you want to mark an error in a method that add two numbers if any of then is negative you can write something like this:

public int addMethod( int a, int b ){

if ( a < 0 b < 0 ){

throw new ArithmeticException("negative addition");

}

return a + b;

}

The previous code cause a ArithmeticException if some try to add negative numbers.

Answer 2

Let's say I have this method:

int returnElementIndex(Element e) throws ElementNotFoundException {

/* code */

}

throws keyword allows us to declare that this method (returnElementIndex) might throw exception (ElementNotFoundException) and every method/peace of code using this function must take care of this exception.

You can't do this:

list.returnElementIndex(someElement);

JAVA compiler is going to give you error, that exception must be caught.

You must always take care of exceptions:

try {

list.returnElementIndex(someElement);

} catch (ElementNotFoundException enfe) {

/* code taking care of this problem */

}