Java multi Generic collection parameters complie error

Posted by Geln Yang on Stack Overflow See other posts from Stack Overflow or by Geln Yang
Published on 2010-05-24T03:30:01Z Indexed on 2010/05/24 3:30 UTC
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Hi,

So strange!Please have a look the code first:

public class A {

}
public class B extends A {

}
public class C extends A {

}
public class TestMain {

    public <T extends A> void test(T a, T b) {

    }

    public <T extends A> void test(List<T> a, List<T> b) {

    }

    public static void main(String[] args) {
        new TestMain().test(new B(), new C());
        new TestMain().test(new ArrayList<B>(), new ArrayList<C>());
    }
}

The statement "new TestMain().test(new ArrayList(), new ArrayList())" get a "Bound mismatch" compile error, while "new TestMain().test(new B(), new C())" is compiled ok.

Bound mismatch: The generic method test(T, T) of type TestMain is not applicable for the arguments (ArrayList, ArrayList). The inferred type ArrayList is not a valid substitute for the bounded parameter

It seems the type of the second generic List parameter is limited by the Type of the first.Is it a feature or a bug of the compile program? ps, jdk:1.6,IDE:Eclipse 3.5.1

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