Java has many built-in exception classes, such as
IllegalArgumentException. At times however, you might want to create your own exception class. For example, as opposed to throwing
IllegalArgumentException when a 0 is detected as a divisor during a division operation, you might wish to throw a
DivideByZeroException. This exception class does not exist in the Java core API, but you can create one yourself. The seven steps below will show you how to create an exception class in Java.
Exceptionclass that is defined in the Java core API (in the package is
java.lang). When extending
Exceptionyou are defining a "checked" exception, i.e., an exception that must be caught or thrown. A constructor is provided that passes the message argument to the super class
Exceptionclass supports a
divideIntmethod must provide a
throwclause because the method potentially throws the
DivideByZeroException. To create the exception object, the program uses the
throwkeyword followed by the instantiation of the exception object. At runtime, the
throwclause will terminate execution of the method and pass the exception to the calling method.
divideIntmethod is successful. The second call, using a divisor of 0, causes the
DivideByZeroExceptionto be thrown in the
divideIntmethod. The message passed to the constructor is displayed in the output.