在If条件下匹配Java中的枚举字符串

Question

I have an enum:

public enum Status{
   A("A"),
   B("B"),
   C("C"),
   D("D"),
   E("E")
}

A,B,C are in one category and D&E are a different category. Now when I get a string, I want to decide which category it falls in. Basically,

String s;
if   s.equals( Status.A.toString()) || s.equals(Status.B.toString()) || s.equals( Status.C.toString()) 
            return 1; 

        else return 2;

Now, this is manageable with 5 letters. If I have 26 letters, the number of if conditions will be unmanageable. Is there a better way to write this?

Answer 1

Rather than deciding the category in the code, store it in the enum itself. You are not limited to a single stored attribute; you can have as many as you wish.

Change the constructor to take the category in addition to the letter, and store it in the enum :

public enum Status {
    A("A", 1),
    B("B", 1),
    C("C", 1),
    D("D", 2),
    E("E", 2);
    private String name;
    private int category;
    public String getName() { return name; }
    public int getCategory() { return category; }
    Status(String name, int category) {
        this.name = name;
        this.category = category;
    }
}

Now it is very clear which enum belongs to what category, because categories are assigned declaratively rather than algorithmically.

Answer 2

How about you maintain a list of enums per category and then compare your string with the enums in a category list? See the following example.

    List<Status> category1 = new ArrayList<Status>();
    category1.add(Status.A);
    category1.add(Status.B);
    category1.add(Status.C);
    List<Status> category2 = new ArrayList<Status>();
    category2.add(Status.D);
    category2.add(Status.E);

    for(Status e : category1) {
        if(s.equals(e.toString()))
            return true;
    }

    for(Status e : category2) {
        if(s.equals(e.toString()))
            return true;
    }

    return false;