EnumMap

EnumMap

    private final Class<K> keyType;

    /**
     * All of the values comprising K.  (Cached for performance.)
     */
    private transient K[] keyUniverse;

    /**
     * Array representation of this map.  The ith element is the value
     * to which universe[i] is currently mapped, or null if it isn't
     * mapped to anything, or NULL if it's mapped to null.
     */
    private transient Object[] vals;

    /**
     * The number of mappings in this map.
     */
    private transient int size = 0;

实现：数组实现

使用案例：

public enum Color {

    red,black,green;

}

Map<Color,String> map = new EnumMap<Color,String>(Color.class);