Convert ENum array to integer value?

Question

I have an enum:

 public enum ScopeItems {
   BASIC_INFO, POLICY_INFO, USER_INFO
 };

And I have a number of Auth objects which might hold any combination of these scopes.

What I want to do is assign an integer value depending on which of these scope items the Auth object holds.

So for example assume:

BASIC_INFO = 1; POLICY_INFO = 2; USER_INFO = 4;

If I have an integer value of 5 then I'd want to return an array with:

BASIC_INFO, USER_INFO

I also want it to work in reverse, so if I pass in an array of POLICY_INFO, USER_INFO I'd get 6 back.

I've got this working, but my solution seemed a bit too complicated for what it is. I'm sure there are better ways of going about it I'm not thinking of.

Еnum is an object. Add field int value to enum class, and create a constructor : ScopeItems(int I){ this.value = I;} -> BASIC_INFO(1), POLICY_INFO(2), USER_INFO(4) ... And you can add a method like public int getValue(){...}. — kozmo
– kozmo, Commented Jan 29, 2018 at 15:30

Ian Mc · Accepted Answer · 2018-01-29 17:04:51Z

3

The following enum should accomplish what you want:

public enum ScopeItems {

    BASIC_INFO(1), POLICY_INFO(2), USER_INFO(4);

    private final int score;
    public int getScore() {
        return score;
    }
    private ScopeItems(int score) {
        this.score = score;
    }

    public static Set<ScopeItems> getScopeByScore(int score) {
        return Stream.of(values()).filter(i -> (i.getScore() | score) == score).collect(Collectors.toSet());
    }

    public static int getScoreByItems(Set<ScopeItems> items) {
        return items.stream().mapToInt(i -> i.getScore()).sum();
    }

};

Efficiency improvement in getScopeByStore() suggested by Klitos:

.collect(Collectors.toSet())   // Inefficient
.collect(Collectors.toCollection(() -> EnumSet.noneOf(ScopeItems.class)) // Better!

And how to use it:

ScopeItems.getScopeByScore(5);   // Returns the Set

ScopeItems.getScoreByItems(EnumSet.of(ScopeItems.BASIC_INFO, ScopeItems.POLICY_INFO))  // Returns the score

There is no current validation; the enum would improve if the methods validated the input.

edited Jan 29, 2018 at 17:04

answered Jan 29, 2018 at 15:47

Ian Mc

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2 Comments

Klitos Kyriacou Over a year ago

It would be nice if getScopeByScore returned an EnumSet, which is more efficient than the type of Set that .collect(Collectors.toSet())) gives you. You can achieve that with .collect(Collectors.toCollection(() -> EnumSet.noneOf(ScopeItems.class))).

user7862512 Over a year ago

Thanks, this works perfectly and was much cleaner than what I was doing! =)

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