Re: Bitwise (flags) enums: how to compare?

From:

Jeffrey Schwab <jeff@schwabcenter.com>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 03 Oct 2006 00:05:37 GMT

Message-ID:

<lPhUg.250$UE6.215@tornado.southeast.rr.com>

z-man wrote:

I tried hard to find on google some reference about bitwise (flags)
native enums in Java 1.5, without success.
What's the proper way to define and compare bitwise enums (see below)?

Thank you!

public enum MyFlags
{
FlagA(1),
FlagB(2);

private final int bit;

MyFlags(int bit)
{
this.bit = bit;
}

public int getBit()
{
return bit;
}
}

....

MyFlags flags = FlagA + FlagB;
// Question: Is this bitwise comparison legal?
if((flags & FlagB) == FlagB)
System.out.println("Caught!");
else
System.out.println("Missed (should not happen).");

java.util.EnumSet may be what you want.

// cljp\MyFlags.java
package cljp;

public enum MyFlags {
     FlagA,
     FlagB
}

// cljp\Main.java
package cljp;

import java.util.EnumSet;
import static cljp.MyFlags.*;

public class Main {

     public static void main(String[] args) {

         EnumSet<MyFlags> flags = EnumSet.of(FlagA, FlagB);

         if(flags.contains(FlagB)) {
             System.out.println("Caught!");
         } else {
             System.out.println("Missed (should not happen).");
         }
     }
}