How to remove a flag in Java

|= performs a bitwise or, so you're effectively "adding" all the flags other than OPTION_E. You want &= (bitwise and) to say you want to retain all the flags other than OPTION_E:

result &= ~OPTION_E;

However, a better approach would be to use enums and EnumSet to start with:

EnumSet<Option> options = EnumSet.of(Option.A, Option.B, Option.C,
                                     Option.D, Option.E);
options.remove(Option.E);

You must write

result &= ~OPTION_E;

Longer explanation:

You must think in bits:

~OPTION_E    // 0x0010 -> 0xFFEF
DEFATUL_OPTIONS //     -> 0x001F
0xFFEF | 0x001F //     -> 0xFFFF
0XFFEF & 0x001F //     -> 0x000F

The OR will never clear 1 bits, it will at most set some more. AND on the other hand will clear bits.