You need to know the size of everything contained within a directory.

Use the sizeOfDirectory( ) method on FileUtils. The following example returns the size of the temp directory:

File dir = new File( "temp" );
long dirSize = FileUtils.sizeOfDirectory( );

If temp contains a number files, FileUtils.sizeOfDirectory( ) will return the sum of the size of every file in temp. If temp contains subdirectories, this method will recursively call sizeOfDirectory( ) on each subdirectory to obtain the size of each subdirectory, and it will return the sum of these sizes.