Question

In application frameworks I keep seeing frameworks that allow you to pass in multiple Int values (generally used in place of an enum) into a function.

For example:

public class Example {      public class Values     {         public static final int ONE = 0x7f020000;         public static final int TWO = 0x7f020001;         public static final int THREE = 0x7f020002;         public static final int FOUR = 0x7f020003;         public static final int FIVE = 0x7f020004;     }      public static void main(String [] args)     {         // should evaluate just Values.ONE         Example.multiValueExample(Values.ONE);          // should evalueate just values Values.ONE,  Values.THREE, Values.FIVE         Example.multiValueExample(Values.ONE | Values.THREE | Values.FIVE);          // should evalueate just values Values.TWO , Values.FIVE         Example.multiValueExample(Values.TWO | Values.FIVE);     }      public static void multiValueExample(int values){         // Logic that properly evaluates bitwise values         ...     } } 

So what logic should exist in multiValueExample for me to properly evaluate multiple int values being passed in using the bitwise operator?

Answer 1

Your values should be powers of 2.

That way, you don’t lose any information when you bitwise-OR them.

public static final int ONE   = 0x01; public static final int TWO   = 0x02; public static final int THREE = 0x04; public static final int FOUR  = 0x08; public static final int FIVE  = 0x10; 

etc.

Then you can do this:

public static void main(String [] args) {     Example.multiValueExample(Values.ONE | Values.THREE | Values.FIVE); }  public static void multiValueExample(int values){     if ((values & Values.ONE) == Values.ONE) {     }      if ((values & Values.TWO) == Values.TWO) {     }      // etc. }