Examines and removes out of date target files. If any of the target files are out of date with respect to any of the source files, all target files are removed. This is useful where dependencies cannot be computed (for example, dynamically interpreted parameters or files that need to stay in synch but are not directly linked) or where the ant task in question could compute them but does not (for example, the linked DTD for an XML file using the style task). nested arguments:

• srcfileset (fileset describing the source files to examine)
• srcfilelist (filelist describing the source files to examine)
• targetfileset (fileset describing the target files to examine)
• targetfilelist (filelist describing the target files to examine)

At least one instance of either a fileset or filelist for both source and target are required.

This task will examine each of the source files against each of the target files. If any target files are out of date with respect to any of the source files, all targets are removed. If any files named in a (src or target) filelist do not exist, all targets are removed. Hint: If missing files should be ignored, specify them as include patterns in filesets, rather than using filelists.

This task attempts to optimize speed of dependency checking. It will stop after the first out of date file is found and remove all targets, rather than exhaustively checking every source vs target combination unnecessarily.

Example uses:

• Record the fact that an XML file must be up to date with respect to its XSD (Schema file), even though the XML file itself includes no reference to its XSD.
• Record the fact that an XSL stylesheet includes other sub-stylesheets
• Record the fact that java files must be recompiled if the ant build file changes