These rules deal with different problems that can occur with finalizers.
If the finalize() method is empty, then it does not need to exist.
This rule is defined by the following XPath expression:
//MethodDeclaration[MethodDeclarator[@Image='finalize'][not(FormalParameters/*)]] /Block[count(*)=0]
Here's an example of code that would trigger this rule:
public class Foo { protected void finalize() {} }
If the finalize() is implemented, it should do something besides just calling super.finalize().
This rule is defined by the following XPath expression:
//MethodDeclaration[MethodDeclarator[@Image="finalize"][not(FormalParameters/*)]] /Block[count(BlockStatement)=1] /BlockStatement[ Statement/StatementExpression/PrimaryExpression /PrimaryPrefix[@Image="finalize"] ]
Here's an example of code that would trigger this rule:
public class Foo { protected void finalize() { super.finalize(); } }
Methods named finalize() should not have parameters. It is confusing and probably a bug to overload finalize(). It will not be called by the VM.
This rule is defined by the following XPath expression:
//MethodDeclaration /MethodDeclarator[@Image='finalize'][FormalParameters[count(*)>0]]
Here's an example of code that would trigger this rule:
public class Foo { // this is confusing and probably a bug protected void finalize(int a) { } }
If the finalize() is implemented, its last action should be to call super.finalize
This rule is defined by the following XPath expression:
//MethodDeclaration[MethodDeclarator[@Image='finalize'][not(FormalParameters/*)]] /Block /BlockStatement[last()] [not(Statement/StatementExpression/PrimaryExpression/PrimaryPrefix[@Image='finalize'])] [not(Statement/TryStatement/FinallyStatement /Block/BlockStatement/Statement/StatementExpression /PrimaryExpression/PrimaryPrefix[@Image='finalize'])]
Here's an example of code that would trigger this rule:
public class Foo { protected void finalize() { something(); // neglected to call super.finalize() } }
If you override finalize(), make it protected. If you make it public, other classes may call it.
This rule is defined by the following XPath expression:
//MethodDeclaration[@Protected="false"] /MethodDeclarator[@Image="finalize"] [not(FormalParameters/*)]
Here's an example of code that would trigger this rule:
public class Foo { public void finalize() { // do something } }
Object.finalize() is called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.AvoidCallingFinalize
Here's an example of code that would trigger this rule:
public class Foo { void foo() { Bar b = new Bar(); b.finalize(); } }