CODEWITHSUNDEEP
javabitmask
mrblah
mrblah

Reputation: 103497

create a permission bit mask in java

I want to do something like this:

public enum Permissions
{
    CanBlah1,
    CanBlah2,
    CanBlah3
}

byte[] userPerm = Permissions.CanBlah1 | Permissions.CanBlah2;

// check permssions
//
if(userPerm && Permissions.CanBlah1 == Permissions.CanBlah1)
{
      // do something
}

Can you do this in Java like that? (I'm coming from a c# background)

Upvotes: 17

Views: 15809

Answers (5)

Roman M
Roman M

Reputation: 12408

If you stuck in the pre Java 7 Era (Android) you can try the following code:

public enum STUFF_TO_BIT_BASK {
THIS,THAT,OTHER;

public static int getBitMask(STUFF_TO_BIT_BASK... masks) {
    int res = 0;

    for (STUFF_TO_BIT_BASK cap : masks) {
        res |= (int) Math.pow(2, cap.ordinal());
    }

    return res;
}

public boolean is(int maskToCheck){
    return maskToCheck | (int) Math.pow(2, this.ordinal());
}

}

Upvotes: 2

TjeerdJan
TjeerdJan

Reputation: 1924

This is another option, which is similar to the ordinal solution, except that you can use the | and & operators with this:

 public enum Permissions {
     CanBlah1(1),
     CanBlah2(2),
     CanBlah3(4);

     public int value;

     Permissions(int value) {
         this.value = value;
     }
     public int value() {
      return value;
     }
 }

 public static void main(String[] args) {  
    int userPerm = Permissions.CanBlah1.value() | Permissions.CanBlah2.value();
    // check permssions
    //
    if((userPerm & Permissions.CanBlah1.value()) == Permissions.CanBlah1.value())
    {
        // do something
    }
 }

or:

 public enum Permissions {
         CanBlah1,
         CanBlah2,
         CanBlah3;

         public int value() {
            return 1<<ordinal();
         }
     }

     public static void main(String[] args) {  
        int userPerm = Permissions.CanBlah1.value() | Permissions.CanBlah2.value();
        // check permssions
        //
        if((userPerm & Permissions.CanBlah1.value()) == Permissions.CanBlah1.value())
        {
            // do something
        }
     }

Upvotes: 7

MeBigFatGuy
MeBigFatGuy

Reputation: 28568

While i wouldn't recommend it, you can ask for the ordinal() of an enum and use that for bit operations. Of course since you can't define what the ordinal is for an enum, you have to insert bogus values to get the ordinals right

enum Example {
   Bogus,            --> 0
   This,             --> 1
   That,             --> 2
   ThisOrThat        --> 3
};

Notice a Bogus enum needed to be introduced so that 

ThisOrThat.ordinal() == This.ordinal() | That.ordinal()

Upvotes: 3

Chandra Patni
Chandra Patni

Reputation: 17577

You can easily do it using EnumSet

import java.util.EnumSet;

import static java.util.EnumSet.of;
import static java.util.EnumSet.range;
import static so.User.Permissions.CanBlah1;
import static so.User.Permissions.CanBlah2;
import static so.User.Permissions.CanBlah3;

public class User {
    public enum Permissions {
        CanBlah1,
        CanBlah2,
        CanBlah3
    }

    public static void main(String[] args) throws Exception {
        EnumSet<Permissions> userPerms = of(CanBlah1, CanBlah2);
        System.out.println(userPerms.contains(CanBlah1)); //true
        System.out.println(userPerms.contains(CanBlah2)); //true
        System.out.println(userPerms.contains(CanBlah3)); //false
        System.out.println(userPerms.containsAll(of(CanBlah1, CanBlah3))); //false
        System.out.println(userPerms.containsAll(range(CanBlah1, CanBlah2))); //true
        System.out.println(userPerms.containsAll(range(CanBlah1, CanBlah3))); //false
    }

}

Upvotes: 38

Upul Bandara
Upul Bandara

Reputation: 5958

As far as I know bitwise operator is undefined for enum types

Upvotes: 0

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