Question

I can’t seem to find any method on FileObject or FileContent which allows me to set a new size on an existing file.

FileContent.getSize() does not have a corresponding setSize(). RandomAccessContent does have some comments about seeking but it does not appear to state that a file will shrink if one seeks somewhere before the end and then simply closes the file.

/**
 * Sets the file-pointer offset, measured from the beginning of this
 * file, at which the next read or write occurs.  The offset may be
 * set beyond the end of the file. Setting the offset beyond the end
 * of the file does not change the file length.  The file length will
 * change only by writing after the offset has been set beyond the end
 * of the file.
 * <br/>
 * <b>Notice: If you use {@link #getInputStream()} you have to reget the InputStream after calling {@link #seek(long)}</b>
 *
 * @param pos the offset position, measured in bytes from the
 *            beginning of the file, at which to set the file
 *            pointer.
 * @throws IOException if <code>pos</code> is less than
 *                     <code>0</code> or if an I/O error occurs.
 */
public void seek(long pos) throws IOException;

Answer 1

using the public APIs you cant set the size or truncate any file. However some specialised types do offer a method that may be used. That said the method may also be not public requiring nasty reflection.