如何存储Java常量以用于构建键值组合

Question

假设我想将这些键的潜在键和潜在值存储为常量.我怎样才能做到这一点？或者我应该完全避免它？

这是我自己想到的方法,但正如你将能够看到的那样,它有明显的垮台.

public static class Foo { 

    public static final String KEY = "foo" ; 

    public static class Values { 

        public static final String BAR = "bar" ; 
        public static final String HEY = "hey" ; 

    }

}

public static class Another { 

    public static final String KEY = "another" ; 

    public static class Values { 

        public static final String ONE = "1" ; 
        public static final String TWO = "two" ;
        public static final String THREE = "THREE" ;

    }

}

这允许我这样访问这些键

miscellaneousMethod( Foo.KEY, Foo.Values.BAR )
miscellaneousMethod( Another.KEY, Another.Values.TWO )

但是,我并不想为每个键/可能值对编写单独的静态内部类.

有没有更好的方法将键值对存储为常量？

我想将它们存储为常量,以便稍后与生成的哈希映射进行比较.所以我可以问这样的东西:

if( map.get( Foo.KEY ).equals( Foo.Values.HEY ) ) { /* do stuff */ }

Answer 1

如果它们都是常量,则可以使用枚举:

public enum ValueEnum {

    FOO("foo", "bar", "hey"),
    ANOTHER("another", "1", "two", "THREE"),

    ;

    private final String key;

    private final Set<String> values;

    private ValueEnum(String key, String... values) {
        this.key = key;
        this.values = Collections.unmodifiableSet(new HashSet<String>(Arrays.asList(values)));
    }

    public final boolean isInMap(Map<String,String> map) {
        if(map.containsKey(key)) {
            return values.contains(map.get(key));
        }
        else {
            return false;
        }
    }
}

然后

if( ValueEnum.FOO.isInMap(map) ) { /* do stuff */ }