question: private static void assertFilesExist ( final List < File > expectedFiles ) { final List < File > missingFiles = new ArrayList < File > ( ) ; for ( final File file : expectedFiles ) { if ( file == null ) { throw new RuntimeException ( "Null passed to assertFilesExist" ) ; } if ( ! file . exists ( ) ) { missingFiles . add ( file ) ; } } if ( ! missingFiles . isEmpty ( ) ) { List < String > missingAbsoluteFilenames = new ArrayList < String > ( missingFiles . size ( ) ) ; for ( File missingFile : missingFiles ) { missingAbsoluteFilenames . add ( missingFile . getAbsolutePath ( ) ) ; } throw new RuntimeException ( "The following files could not be located: " + PluginUtil . join ( ", " , missingAbsoluteFilenames ) ) ; } }
target:  Assert that all files in the list exist and if they don't, throw a RuntimeException with a list of the files that do not exist.