无涯教程-Java泛型 - 命名约定按照惯例，类型参数名称被命名为单个大写字母，以便可以使用普通的类或接口名称区分类型

按照惯例，类型参数名称被命名为单个大写字母，以便可以使用普通的类或接口名称区分类型参数。以下是常用类型参数名称的列表-

E 元素 - 主要由Java Collections框架使用。
K 键 - 主要用于表示Map键的参数类型。
V 值 - 主要用于表示Map的值的参数类型。
N 数字 - 主要用于表示数字。
T 类型 - 主要用于表示第一个通用类型参数。
S 类型 - 主要用于表示第二个泛型类型参数。
U 类型 - 主要用于表示第三个通用类型参数。
V 类型 - 主要用于表示第四个泛型类型参数。

以下示例将展示上述概念。

使用您选择的任何编辑器创建以下Java程序。

package com.learnfk;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class GenericsTester {
public static void main(String[] args) {
Box<Integer, String> box = new Box<Integer, String>();
box.add(Integer.valueOf(10),"Hello World");
System.out.printf("Integer Value :%d\n", box.getFirst());
System.out.printf("String Value :%s\n", box.getSecond());
  </span><span class="typ">Pair</span><span class="pun">&lt;</span><span class="typ">String</span><span class="pun">,</span><span class="pln"> </span><span class="typ">Integer</span><span class="pun">&gt;</span><span class="pln"> pair </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Pair</span><span class="pun">&lt;</span><span class="typ">String</span><span class="pun">,</span><span class="pln"> </span><span class="typ">Integer</span><span class="pun">&gt;();</span><span class="pln"> 
  pair</span><span class="pun">.</span><span class="pln">addKeyValue</span><span class="pun">(</span><span class="str">"1"</span><span class="pun">,</span><span class="pln"> </span><span class="typ">Integer</span><span class="pun">.</span><span class="pln">valueOf</span><span class="pun">(</span><span class="lit">10</span><span class="pun">));</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">printf</span><span class="pun">(</span><span class="str">"(Pair)Integer Value :%d\n"</span><span class="pun">,</span><span class="pln"> pair</span><span class="pun">.</span><span class="pln">getValue</span><span class="pun">(</span><span class="str">"1"</span><span class="pun">));</span><span class="pln">

  </span><span class="typ">CustomList</span><span class="pun">&lt;</span><span class="typ">Box</span><span class="pun">&gt;</span><span class="pln"> list </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">CustomList</span><span class="pun">&lt;</span><span class="typ">Box</span><span class="pun">&gt;();</span><span class="pln">
  list</span><span class="pun">.</span><span class="pln">addItem</span><span class="pun">(</span><span class="pln">box</span><span class="pun">);</span><span class="pln">
  </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">printf</span><span class="pun">(</span><span class="str">"(CustomList)Integer Value :%d\n"</span><span class="pun">,</span><span class="pln"> list</span><span class="pun">.</span><span class="pln">getItem</span><span class="pun">(</span><span class="lit">0</span><span class="pun">).</span><span class="pln">getFirst</span><span class="pun">());</span><span class="pln">

}
}
class Box<T, S> {
private T t;
private S s;
public void add(T t, S s) {
this.t = t;
this.s = s;
}
public T getFirst() {
return t;
}
public S getSecond() {
return s;
}
}
class Pair<K,V>{
private Map<K,V> map = new HashMap<K,V>();
public void addKeyValue(K key, V value) {
map.put(key, value);
}
public V getValue(K key) {
return map.get(key);
}
}
class CustomList<E>{
private List<E> list = new ArrayList<E>();
public void addItem(E value) {
list.add(value);
}
public E getItem(int index) {
return list.get(index);
}
}

这将产生以下输出。

Integer Value :10
String Value :Hello World
(Pair)Integer Value :10
(CustomList)Integer Value :10

无涯教程-Java泛型 - 命名约定

参考链接