Java check if flags are set in integer

Question

I've got a feeling the answer to this is to bit shift, but I can't quite get my brain to grasp it.

I've got some integer values being read, always different, and I need to check if some flags are set by looking at their bit pattern, for example.

Flags:
0x00000002 = Do thing 
0x80000000 = Do another thing

Value: 0x80000002

So looking at the value, both flags should be set. But I'm not sure of the best way to implement this. I guess I could use BigInteger.testBit();, but I don't really want to have to figure out the exact bit in each of the flags (there are a lot).

I can remember doing something like this in C a long time ago, it was something like if (value & flag), but Java doesn't seem to like this.

Any ideas of suggestions, would be greatly appreciated.

Thanks

score 4 · Answer 1 · edited May 30 '18 at 15:47

4

If you want to use bits, you could use AND

boolean isSet = (values & mask) == mask;

But for a very, very small performance hit (probably not big enough to notice) you can get this same basic principle with EnumSet

boolean isSet = myEnumSet.contains(MyEnumReferencingTheOldIntegerValue)

edited May 30 '18 at 15:47

BackSlash

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answered May 30 '18 at 15:45

corsiKa

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Thanks, I think this will do the trick. I'll also take a look into the EnumSet. – Tony May 30 '18 at 15:57

score 1 · Answer 2 · answered May 30 '18 at 15:47

1

Probably the easiest solution is the following:

if ((value & 0x00000002) != 0)
    // Do thing
if ((value & 0x80000000) != 0)
    // Do other thing

You just have to make sure that you're only using one bit per flag. If you are, it's more complicated.

answered May 30 '18 at 15:47

Raceimaztion

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Java check if flags are set in integer

2 Answers2