Object Oriented Programming

Throwing an Exception in Java

Methods prone to an error in runtime can throw an exception, instead of having program crash or having a logical error within the program.

Syntax

public methodName function throws exceptionName{
    //checking for regular or error condition
    if(booleanExpression){ //good condition
    }
    else { //error condition
         throw new exceptionName();
    }
}

Notes

Exceptions are typically thrown when a method itself doesn't handle a checked exception.

Example

public createArray() throws ArrayIndexOutOfBoundsException{
    int[] array = new int[3];
    int index = 7;
    if(index < array.length){
        array[index] = 3;
    }
    else {
        throw new ArrayIndexOutOfBoundsException();
    }
}

See Also

Declaring an Exception

How to Throw Exceptions - Java Tutorials
Specifying the Exceptions Thrown by the Method