Understanding Generics in Java Methods

The presence of multiple "return types" in a Java method definition can seem puzzling. Let's delve into an example:

public  List getResult(String s);

where Foo is a class you have defined.

Question: What is the Return Type of This Method?

Answer: This method has a single return type: List.

Question: Why Does It Seem to Have Two Return Types?

Answer: The method utilizes generics, a powerful feature in Java that allows for the creation of methods that work with different types by using type parameters. In this case:

• : This part declares a generic type for the method. It means the method can accept any type parameter E that is a subclass of Foo.
• List: This is the actual return type of the method. It returns a list of objects of type E, which can be any subclass of Foo.

In essence, the method declares that it can work with any type that extends Foo and returns a list of such types. This provides flexibility and type safety, ensuring that the returned list contains only objects that are subclasses of Foo.