Generic static methods within a generic class

Question

Suppose I have:

public class Parent<T extends Child1>  {
    public Parent() {       
    }

    public static <T extends Number> void test(T t) {
    }
}

And Child1 is a child class of Parent.

What I'm trying to understand here is the connection between the parameter type T in both class scope and method scope. How can both parameters (class' and method's) be allowed to be named T if their bounds are completely different from one another?

Rohit Jain · Accepted Answer · 2015-04-18 05:01:34Z

6

The type parameter defined in the method is completely independent of the one defined in the class. In fact, you've to define type parameter for static methods, as class-level type parameters can't be used there. You can't use class-level type parameter in static context. That's outside their scope. So, if you remove that method level type parameter declaration, you'll get a compilation error.

answered Apr 18, 2015 at 5:01

Rohit Jain

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3 Comments

Dimitri Over a year ago

This just summed it up for me!

Dimitri Over a year ago

One last thing. Does the same apply for non-static methods, or is defining a generic parameter on a method always exclusive to that method, regardless of their visibility?

Rohit Jain Over a year ago

@Dimitri Yes, defining a type parameter on any method is independent of the one defined in class.

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