Menu
I'm learning Java generics and I ask myself this question.
What is the difference between these two method declarations?
public static void someMethod(List<? extends Number> numberList); and
public static <E extends Number> void someMethod(List<E> numberList); 
950
A Generic class can have muliple type parameters.
For static generic methods, the type parameter section must appear before the method's return type. The complete syntax for invoking this method would be: Pair<Integer, String> p1 = new Pair<>(1, "apple"); Pair<Integer, String> p2 = new Pair<>(2, "pear"); boolean same = Util. <Integer, String>compare(p1, p2);
In a nutshell, generics enable types (classes and interfaces) to be parameters when defining classes, interfaces and methods. Much like the more familiar formal parameters used in method declarations, type parameters provide a way for you to re-use the same code with different inputs.
A generic method can also be overloaded by nongeneric methods. When the compiler encounters a method call, it searches for the method declaration that best matches the method name and the argument types specified in the call—an error occurs if two or more overloaded methods both could be considered best ...
In the latter you have a reference to the type within the scope of someMethod, namely E. In the former you do not.
172
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
