public boolean get(int index) {
        assert index >= 0 && index < (wlen << 6);

        int i = index >> 6; // div 64
        // signed shift will keep a negative index and force an
        // array-index-out-of-bounds-exception, removing the need for an explicit check.
        if (i >= wlen) return false;

        int bit = index & 0x3f; // mod 64
        long bitmask = 1L << bit;
        return (word(i) & bitmask) != 0;
    }
@param index The index.
@return Returns true or false for the specified bit index.
indexr-common/src/main/java/io/indexr/util/DirectBitMap.java