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():
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.Testpublic 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.Testpublic 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
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:
提供了很多静态的构建方法:
简单的构建方法测试:
@org.junit.Testpublic 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:
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