你的位置:首页 > Java教程

[Java教程]【JAVA集合】EnumMap


以下内容基于jdk1.7.0_79源码;

什么是EnumMap

Map接口的实现,其key-value映射中的key是Enum类型;

补充说明

其原理就是一个对象数组,数组的下标索引就是根据Map中的key直接获取,即枚举中的ordinal值;

效率比HashMap高,可以直接获取数组下标索引并访问到元素;

简单示例

比较简单,源代码就不一一添加注释了,简单地说,就是一个对象数组;

这里稍微了解一下怎么使用就好了,下面列出一些方法的调用示例:

package com.pichen.collection;import java.util.EnumMap;import java.util.Map;import java.util.Map.Entry;enum Operate{  ADD, UPDATE, DELETE; }public class Main {  public static void main(String[] args) {    Map<Operate, String> map = new EnumMap<Operate, String>(Operate.class);    //put方法    map.put(Operate.ADD, "add operate");    map.put(Operate.UPDATE, "update operate");    map.put(Operate.DELETE, "delete operate");        //重写了toString方法    System.out.println(map);        //size方法    System.out.println(map.size());        System.out.println(map.containsKey(Operate.UPDATE));    System.out.println(map.containsValue("update operate"));    System.out.println(map.get(Operate.DELETE));        //remove    map.remove(Operate.UPDATE);    System.out.println(map);        //key集合    for(Operate operate:map.keySet()){      System.out.print(operate + " ");    }        System.out.println();    //value集合    for(String obj:map.values()){      System.out.print(obj + ",");    }        System.out.println();    //key-value集合    for(Entry<Operate, String> entry:map.entrySet()){      System.out.print(entry.getKey() + ": " + entry.getValue() + ", ");    }  }}

输出结果:

{ADD=add operate, UPDATE=update operate, DELETE=delete operate}3truetruedelete operate{ADD=add operate, DELETE=delete operate}ADD DELETE add operate,delete operate,ADD: add operate, DELETE: delete operate,