code: static JarFileWithEntryClass findOnlyEntryClass(Iterable<File> jarFiles) throws IOException {
  		List<JarFileWithEntryClass> jarsWithEntryClasses = new ArrayList<>();
  		for (File jarFile : jarFiles) {
  			findEntryClass(jarFile)
  				.ifPresent(entryClass -> jarsWithEntryClasses.add(new JarFileWithEntryClass(jarFile, entryClass)));
  		}
  		int size = jarsWithEntryClasses.size();
  		if (size == 0) {
  			throw new NoSuchElementException("No JAR with manifest attribute for entry class");
  		}
  		if (size == 1) {
  			return jarsWithEntryClasses.get(0);
  		}
  		// else: size > 1
  		throw new IllegalArgumentException("Multiple JARs with manifest attribute for entry class: "
  			+ jarsWithEntryClasses);
  	}
docs: Returns a JAR file with its entry class as specified in the manifest.
  
  @param jarFiles JAR files to parse
  
  @throws NoSuchElementException if no JAR file contains an entry class attribute
  @throws IllegalArgumentException if multiple JAR files contain an entry class manifest attribute