EnumMap,EnumSet枚举操作类的简单使用

心已赠人 2023-02-24 11:12 95阅读 0赞

## 首先说EnumMap ##

这个类,1.5就出了,继承AbstractMap,说白了就是个map,只是他的key是枚举:  
Enummap也是线程不安全的,内部实现了迭代器,如果有线程安全问题,记得转迭代器,使用这个方法转就好enumMap.entrySet().iterator():

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 1]  
使用就是直接当做map就好了,为啥要使用这个类,很简单,快,进行了部分优化,所以当key为枚举的时候尽量使用这个类:

@org.junit.Test
      public void test2() { 
        EnumMap<Season, String> enumMap = new EnumMap<>(Season.class);
        HashMap<Season, String> aaa = new HashMap();
        enumMap.put(Season.SPRING, "春天");
        enumMap.put(Season.SUMMER, "夏天");
        enumMap.put(Season.AUTUMN, "秋天");
        enumMap.put(Season.WINTER, "冬天");
        System.out.println(enumMap);
        aaa.put(Season.SPRING, "春天");
        aaa.put(Season.SUMMER, "夏天");
        aaa.put(Season.AUTUMN, "秋天");
        aaa.put(Season.WINTER, "冬天");
        System.out.println(aaa);
      }
    
    enum Season { 
      SPRING, SUMMER, AUTUMN, WINTER;
    }

性能比较测试:

@org.junit.Test
      public void test3() { 
        EnumMap<Season, String> enumMap = new EnumMap<>(Season.class);
        HashMap<Season, String> aaa = new HashMap();
        long l = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) { 
          enumMap.put(Season.SPRING, "春天");
          enumMap.put(Season.SUMMER, "夏天");
          enumMap.put(Season.AUTUMN, "秋天");
          enumMap.put(Season.WINTER, "冬天");
          enumMap.remove(Season.SPRING);
          enumMap.remove(Season.SUMMER);
          enumMap.remove(Season.AUTUMN);
          enumMap.remove(Season.WINTER);
        }
        long l2 = System.currentTimeMillis();
        System.out.println(l2 - l);
    
        long l3 = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) { 
          aaa.put(Season.SPRING, "春天");
          aaa.put(Season.SUMMER, "夏天");
          aaa.put(Season.AUTUMN, "秋天");
          aaa.put(Season.WINTER, "冬天");
          aaa.remove(Season.SPRING);
          aaa.remove(Season.SUMMER);
          aaa.remove(Season.AUTUMN);
          aaa.remove(Season.WINTER);
        }
        long l4 = System.currentTimeMillis();
        System.out.println(l4 - l3);
    
      }

执行结果:快乐一倍左右吧  
![在这里插入图片描述][20200709104651674.png]

## 再说EnumSet ##

跟enummap差不多,大部分方法跟Set差不多,只不过构建方法加了很多:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 2]  
提供了很多静态的构建方法:  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 3]  
简单的构建方法测试:

@org.junit.Test
      public void test1() { 
        //创建一个EnumSet集合，集合元素就是Season枚举类的全部枚举值
        EnumSet es = EnumSet.allOf(Season.class);
        System.out.println(es);
    
        //创建一个EnumSet空集合，只顶其集合元素是Season类的枚举值
        EnumSet es2 = EnumSet.noneOf(Season.class);
        System.out.println(es2);
    
        //以枚举值来创建EnumSet集合
        EnumSet es3 = EnumSet.of(Season.SUMMER, Season.WINTER);
        System.out.println(es3); //输出[SUMMER, WINTER]
    
        //创建一个包含Season枚举值从SUMMER到WINTER的EnumSet集合
        EnumSet es4 = EnumSet.range(Season.SUMMER, Season.WINTER);
        System.out.println(es4);//输出[SUMMER, Fall, WINTER]
    
        //创建一个EnumSet集合，其元素和es4集合元素类型相同， es4元素+es5元素=Sesson枚举的全部枚举值
        EnumSet es5 = EnumSet.complementOf(es4);
        System.out.println(es5);//输出[SPRING]
      }

执行结果:

![在这里插入图片描述][20200709105419452.png]

***其他方法就很简单,跟set一样,只不过还是对枚举有优化;所以,如果有枚举set尽量使用这两个类***

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70]: /images/20230209/678482cd71044306b6c61264198edbd5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200709104518440.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70
[20200709104651674.png]: https://img-blog.csdnimg.cn/20200709104651674.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200709104835132.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20200709105233282.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MzY2MDYz,size_16,color_FFFFFF,t_70
[20200709105419452.png]: https://img-blog.csdnimg.cn/20200709105419452.png