Method sizeIfKnown

guava/src/com/google/common/io/ByteSource.java:181–183

Returns the size of this source in bytes, if the size can be easily determined without actually opening the data stream. <p>The default implementation returns {@link Optional#absent}. Some sources, such as a file, may return a non-absent value. Note that in such cases, it is <i>possible</i> that th

()

   * @since 19.0
   */
  public Optional<Long> sizeIfKnown() {
    return Optional.absent();
  }

  /**
   * Returns the size of this source in bytes, even if doing so requires opening and traversing an