PMD Coding practices - Exception handling

Exception handling - rules provided by PMD

Strict Exceptions

AvoidCatchingThrowable

Catching Throwable errors is not recommended since its scope is very broad.

It includes runtime issues such as OutOfMemoryError that should be exposed and managed separately.

SignatureDeclareThrowsException

Methods that declare the generic Exception as a possible throwable are not very helpful since their failure modes are unclear.

Use a class derived from RuntimeException or a more specific checked exception.

ExceptionAsFlowControl

Using Exceptions as form of flow control is not recommended as they obscure true exceptions when debugging.

Either add the necessary validation or use an alternate control structure.

AvoidCatchingNPE

Code should never throw NullPointerExceptions under normal circumstances.

A catch block may hide the original error, causing other, more subtle problems later on.

AvoidThrowingRawExceptionTypes

Avoid throwing certain exception types.

Rather than throw a raw RuntimeException, Throwable, Exception or Error, use a subclassed exception or error instead.

AvoidThrowingNullPointerException

Avoid throwing NullPointerExceptions.

These are confusing because most people will assume that the virtual machine threw it.

Consider using an IllegalArgumentException instead; this will beclearly seen as a programmer-initiated exception.

AvoidRethrowingException

Catch blocks that merely rethrow a caught exception only add to code size and runtime complexity.

DoNotExtendJavaLangError

Errors are system exceptions. Do not extend them.

DoNotThrowExceptionInFinally

Throwing exceptions within a 'finally' block is confusing since they may mask other exceptions or code defects.

Note: This is a PMD implementation of the Lint4j rule "A throw in a finally block"

AvoidThrowingNewInstanceOfSameException

Catch blocks that merely rethrow a caught exception wrapped inside a new instance of the same type only add tocode size and runtime complexity.

AvoidCatchingGenericException

Avoid catching generic exceptions such as NullPointerException, RuntimeException, Exception in try-catch block

AvoidLosingExceptionInformation

Statements in a catch block that invoke accessors on the exception without using the informationonly add to code size.

Either remove the invocation, or use the return result.