java - 方法签名中的 是什么？

Question

我正在从 here 阅读有关 Set 接口(interface)的内容下面的代码是从集合中删除重复项的通用方法。

我的问题是那是什么 **< E>**放置在 static 之后 Set<E> 之前？

我的意思是不是 Set<E>足够 ？为什么<E>有两次吗？

public static <E> Set<E> removeDups(Collection<E> c) {
    return new LinkedHashSet<E>(c);
}

Answer 1

这里**<E>**是一个泛型类型。泛型类型定义为

A generic type is a generic class or interface that is parameterized over types. The following Box class will be modified to demonstrate the concept. LINK

关于您与 <E> 相关的问题。可以在同一个教程中找到对其的详细描述

类型参数命名约定

By convention, type parameter names are single, uppercase letters. This stands in sharp contrast to the variable naming conventions that you already know about, and with good reason: Without this convention, it would be difficult to tell the difference between a type variable and an ordinary class or interface name.

The most commonly used type parameter names are:

 E - Element (used extensively by the Java Collections Framework)
    K - Key
    N - Number
    T - Type
    V - Value
    S,U,V etc. - 2nd, 3rd, 4th types

You'll see these names used throughout the Java SE API and the rest of this lesson.