Difference between java.lang.RuntimeException and java.lang.Exception
Generally RuntimeExceptions are exceptions that can be prevented programmatically. E.g NullPointerException
, ArrayIndexOutOfBoundException
. If you check for null
before calling any method, NullPointerException
would never occur. Similarly ArrayIndexOutOfBoundException
would never occur if you check the index first. RuntimeException
are not checked by the compiler, so it is clean code.
EDIT : These days people favor RuntimeException
because the clean code it produces. It is totally a personal choice.
In Java, there are two types of exceptions: checked exceptions and un-checked exceptions. A checked exception must be handled explicitly by the code, whereas, an un-checked exception does not need to be explicitly handled.
For checked exceptions, you either have to put a try/catch block around the code that could potentially throw the exception, or add a "throws" clause to the method, to indicate that the method might throw this type of exception (which must be handled in the calling class or above).
Any exception that derives from "Exception" is a checked exception, whereas a class that derives from RuntimeException is un-checked. RuntimeExceptions do not need to be explicitly handled by the calling code.