question: protected boolean filterFiles ( List < File > files ) { if ( task . getNoMtimeCheck ( ) || isOutputRepositoryURL ( ) ) { return false ; } Iterator < File > iter = files . iterator ( ) ; while ( iter . hasNext ( ) ) { File file = iter . next ( ) ; Module module = inferModule ( file ) ; if ( module == null ) { task . log ( "Unable to determine module of " + file , Project . MSG_VERBOSE ) ; continue ; } if ( module . getVersion ( ) == null ) { task . log ( "Unable to determine version (and hence timestamp) of " + module . getName ( ) , Project . MSG_VERBOSE ) ; continue ; } long oldest = getArtifactFileTime ( module , file ) ; if ( oldest == Long . MAX_VALUE ) { File outModuleDir = getArtifactDir ( module ) ; oldest = oldestOutputArtifact ( Long . MAX_VALUE , outModuleDir ) ; task . log ( "Oldest file for " + module + " " + new Date ( oldest ) , Project . MSG_DEBUG ) ; } else { task . log ( "Artifact file associated with " + file + " for " + module + " " + new Date ( oldest ) , Project . MSG_DEBUG ) ; } long newestFile = file . lastModified ( ) ; task . log ( "File " + file + " last modified " + new Date ( newestFile ) , Project . MSG_DEBUG ) ; if ( newestFile != Long . MIN_VALUE && oldest != Long . MAX_VALUE && newestFile < oldest ) { task . log ( "No need to compile " + file + ", it's up to date" ) ; iter . remove ( ) ; } } return files . size ( ) == 0 ; }
target:  Filters out all the source files which appear to not require  compilation based on comparison of file modification times