Re: Generics headache

Lew <com.lewscanon@lew>
Sun, 27 Jul 2008 00:10:50 -0400
Leonardo Teixeira Passos wrote:

Hi all. I am currently writing a Java code that looks like the following:

public abstract class Parser {
   abstract public AST parse
    (Scanner scanner,
    Map<String, LinkedList<String> > parameters)
    throws Exception, ParseException, ScanException ; ....

When writing a subclass of Parser, for instance, CupParser, I have:

public class CupParser extends Parser {
    public AST parse
          (Scanner scanner,
       Map<String, LinkedList<Object,String>> parameters)
       throws Exception, ParseException, ScanException {

When using the open-jdk version of javac, it reports the following:

CupParser is not abstract and does not override abstract method
parse(dcf.frontend.Scanner, java.util.Map).

Of course, changing the signature of the parse method to the one stated
by the compiler works fine, but the question is: why does the compiler
complain about the presented code in the subclass, since it is just
restating the inherited method signature?

Does 'CupParser' ensure that 'Scanner' is 'dcf.frontend.Scanner'?

The expression 'LinkedList<Object,String>' should have raised a compiler stink
of its own. LinkedList<T> takes a single parameterized type.

I was going to ask what regular 'javac' reports, but the bad List declaration
is already a problem.

Give us an SSCCE. That will solve the problem before you even post the result.



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