What does <T extends mean?

Question

I have seen a method like shown below:

protected  T save( T Acd, boolean en) {

What does it do? What is these type of

Answer 1

This is called generics in Java.

Official explanation:

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. The difference is that the inputs to formal parameters are values, while the inputs to type parameters are types.

Informally:

Strongly typed languages like Java cause more errors show up at compile time instead of runtime. This is a good thing. But it causes code duplication. To mitigate this generics was added to Java.