private void setBit(int bitIndex) {
    int unitIndex = unitIndex(bitIndex);
    long bit = bit(bitIndex);
    units[unitIndex] |= bit;
  }
Sets the bit at the specified index to <code>true</code> if it is not already in the set.
Otherwise does nothing.

@param bitIndex a bit index.
@exception IndexOutOfBoundsException if the specified index is negative.
geode-core/src/main/java/org/apache/geode/internal/UniqueIdGenerator.java