What is the point of T extends SomeClass?

generics, java

Solution

In your case it doesn't make much difference.

But consider the following:

public <T extends SomeClass> void doSomething(List<T> obj)

In this case you could call the method the following ways:

obj.doSomething(new ArrayList<SubclassOfSomeClass>());
obj.doSomething(new ArrayList<SomeClass>());

If you would use

public void doSomething(List<SomeClass> obj)

You would only be able to do this:

obj.doSomething(new ArrayList<SomeClass>());

Problem

What is the difference with a method declaration like this: ``` public <T extends SomeClass> void doSomething(T obj) { // Do something. } ``` And this: ``` public void doSomething(SomeClass obj) { // Do Something. } ``` The way I see it, both of them are specifying that the object passed in must be a subclass of type `SomeClass`, so why bother with the generics at all in this instance?

Original source

Related problems