Optional boolean argument for a java method:

void testOptionalArgument(boolean ... flag) {
    if (flag == null) {
        log.info("optional flag null");
    } else {
        int length = flag.length;
        log.info("optional flag: " + flag + " length: " + length);
        if (length > 0) {
            log.info("optional flag: " + flag[0]);
        }
    }
}

Calling this method in 3 different ways:

testOptionalArgument(); // optional flag: [Z@ed3c51 length: 0
testOptionalArgument(true);  // optional flag: [Z@1131359 length: 1 optional flag: true
testOptionalArgument(false); // optional flag: [Z@15b3baf length: 1 optional flag: false