编译时引用类型相等

Question

I came across following statement in Java Language Specification-8.It states that 2 classes are same at compile time if:

1. They have same binary name(Canonical Name for outer classes).
2. Their type arguments are same (if any).

Java Spec Doc

But why does compiler raises a duplicate class error for

class Test<String>{
    ...
}

class Test<Integer>{
    ...
}

Here binary name is same but argument types are different.What am I missing here?

Answer 1

It is not the argument, but the Type of a generic class. This type information is removed at runtime, so from a JVM point of view it is identical.

You can read more about Generics and Type Erasure in the Oracle docs .