code: public double getDouble(int index)
      {
          checkIndexLength(index, SizeOf.SIZE_OF_DOUBLE);
          return unsafe.getDouble(base, address + index);
      }
docs: Gets a 64-bit double at the specified absolute {@code index} in
  this buffer.
  
  @throws IndexOutOfBoundsException if the specified {@code index} is less than {@code 0} or
  {@code index + 8} is greater than {@code this.length()}