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[@Finally='true'] /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() } }
An explicit call was made to a finalize method. Finalize methods are meant to be executed at most once (by the garbage collector). Calling it explicitly could result in the method being executed twice for that object (once by you, once by the garbage collector).
This rule is defined by the following XPath expression:
//PrimaryExpression[PrimarySuffix /Arguments[count(*) = 0]] /PrimaryPrefix /Name[@Image = 'finalize' or ends-with(@Image, '.finalize')]
Here's an example of code that would trigger this rule:
public class Foo { public void close() { finalize(); // this is bad foo.finalize(); // this is also bad this.finalize(); // this is bad but currently not flagged super.finalize(); // this is OK foo.finalize(3); // this is arguably OK because the method is overloaded } }
If you override finalize(), make it protected. Otherwise, subclasses may not called your implementation of finalize.
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 } }