java 什么是静态<T> List<T> methodName (List<? super T> input)
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What is static <T> List<T> methodName (List<? super T> input)
提问by user1459497
I have the following code but i am confused with all the generics.
我有以下代码，但我对所有泛型感到困惑。
public static <T> List<T> backwards (List<? super T> input) {
List<T> output = new ArrayList<T>();
return output;
}
My understanding is that I have a public method named backwardswhich creates an arraylist implementing the List interface and returning the arraylist. My question is what actually I am saying to the compiler with the following part......
我的理解是，我有一个名为的公共方法backwards，它创建一个实现 List 接口的数组列表并返回数组列表。我的问题是我实际上是在用以下部分对编译器说些什么......
static <T> List<T> backwards (List<? super T> input)
回答by Paul Bellora
You are saying to the compiler:
你对编译器说：
<T>
"I'm declaring an arbitrary type Tfor this method, which can be anything (non-primitive) for each call of the method."
“我T为这个方法声明了一个任意类型，对于方法的每次调用，它可以是任何（非原始）类型。”
List<T>
"This method will return a Listcontaining elements of that type T."
“此方法将返回List包含该类型的元素T。”
List<? super T> input
"This method will take a parameter called input, which is a Listcontaining elements of type T, or any super-type of T. For example, if Tis Integer, inputcould be a List<Integer>, List<Number>, or List<Object>."
“这种方法将需要一个名为参数input，这是一种List类型的包含元素T，或任何超类型的T。例如，如果T是Integer，input可以是一个List<Integer>，List<Number>或List<Object>”。
回答by jax
This is how you declare Generic Methods. Please read the following part and it will give you everything you need.
这就是您声明泛型方法的方式。请阅读以下部分，它将为您提供所需的一切。
http://docs.oracle.com/javase/tutorial/extra/generics/methods.html
http://docs.oracle.com/javase/tutorial/extra/generics/methods.html
