These rules provide some strict guidelines about throwing and catching exceptions.
This is dangerous because it casts too wide a net; it can catch things like OutOfMemoryError.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.strictexception.AvoidCatchingThrowable
Here's an example of code that would trigger this rule:
public class Foo {
public void bar() {
try {
// do something
} catch (Throwable th) { //Should not catch throwable
th.printStackTrace();
}
}
}
It is unclear which exceptions that can be thrown from the methods. It might be difficult to document and understand the vague interfaces. Use either a class derived from RuntimeException or a checked exception.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.strictexception.ExceptionSignatureDeclaration
Here's an example of code that would trigger this rule:
public void methodThrowingException() throws Exception {
}
Using Exceptions as flow control leads to GOTOish code and obscures true exceptions when debugging.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.design.ExceptionAsFlowControl
Here's an example of code that would trigger this rule:
public class Foo {
void bar() {
try {
try {
} catch (Exception e) {
throw new WrapperException(e);
// this is essentially a GOTO to the WrapperException catch block
}
} catch (WrapperException e) {
// do some more stuff
}
}
}
Code should never throw NPE under normal circumstances. A catch block may hide the original error, causing other more subtle errors in its wake.
This rule is defined by the following XPath expression:
//CatchStatement/FormalParameter/Type
/ReferenceType/ClassOrInterfaceType[@Image='NullPointerException']
Here's an example of code that would trigger this rule:
public class Foo {
void bar() {
try {
// do something
} catch (NullPointerException npe) {
}
}
}
Avoid throwing certain exception types. Rather than throw a raw RuntimeException, Throwable, Exception, or Error, use a subclassed exception or error instead.
This rule is defined by the following XPath expression:
//AllocationExpression
/ClassOrInterfaceType[
@Image='Throwable' or
@Image='Exception' or
@Image='Error' or
@Image='RuntimeException']
Here's an example of code that would trigger this rule:
public class Foo {
public void bar() throws Exception {
throw new Exception();
}
}
Avoid throwing a NullPointerException - it's confusing because most people will assume that the virtual machine threw it. Consider using an IllegalArgumentException instead; this will be clearly seen as a programmer-initiated exception.
This rule is defined by the following XPath expression:
//AllocationExpression/ClassOrInterfaceType[@Image='NullPointerException']
Here's an example of code that would trigger this rule:
public class Foo {
void bar() {
throw new NullPointerException();
}
}
Catch blocks that merely rethrow a caught exception only add to code size and runtime complexity.
This rule is defined by the following XPath expression:
//CatchStatement[FormalParameter
/VariableDeclaratorId/@Image = Block/BlockStatement/Statement
/ThrowStatement/Expression/PrimaryExpression[count(PrimarySuffix)=0]/PrimaryPrefix/Name/@Image
and count(Block/BlockStatement/Statement) =1]
Here's an example of code that would trigger this rule:
public class Foo {
void bar() {
try {
// do something
} catch (SomeException se) {
throw se;
}
}
}