通用和方法

Question

Why do I have to do like this?

public <T> void myMethod(MyClass<T> value){

}

Why do I have to mention <T> twice?

Answer 1

The first <T> declares your method as having a generic parameter.

The second <T> specified the value of the generic parameter for the MyClass<> class. (just like MyClass<string> )

Answer 2

the first <T> declares that you are using a templated method. It is just as proper to say the following:

public void myMethod(MyClass<?> value){

}

You can also declare the generic parameter on the class level like so:

public class MyClass<T> {

    public void myMethod(MyClass<T> value){
    }
}

Answer 3

The outer <T> says 'this is a generic method' and also gives you the chance to place bounds on T, for example T extends Comparable<T>. You wouldn't want to be repeating all that for every parameter that used T.

Answer 4

实际上是第一个限定有在你的函数被使用的通用类和第二MyClass<T>值表示，所述类型类它的T像List<String>其中String可以是你的T 。