private Collection getClassesForCurrentJavaVersion()

in core/src/main/java/com/spotify/missinglink/ArtifactLoader.java [87:138]
43 lines of code
9 McCabe index (conditional complexity)

  private Collection<JarEntry> getClassesForCurrentJavaVersion(Iterable<JarEntry> entries) {
    // First categorize all the found class files by their target JVM
    // classFilesPerJavaVersion: target JVM version -> normalized full name -> JarEntry
    SortedMap<Integer, Map<String, JarEntry>> classFilesPerJavaVersion = new TreeMap<>();
    String patternString = "META-INF/versions/(\\d+)/";
    Pattern pattern = Pattern.compile(patternString);
    for (JarEntry entry : entries) {
      String fileFullName = entry.getName();
      if (fileFullName.endsWith(".class")) {
        Matcher m = pattern.matcher(fileFullName);
        if (m.find()) {
          Integer targetJavaVersion = Integer.parseInt(m.group(1));
          String normalizedFileFullName = fileFullName.replaceAll(patternString, "");

          if (!classFilesPerJavaVersion.containsKey(targetJavaVersion)) {
            classFilesPerJavaVersion.put(targetJavaVersion, new HashMap<>());
          }
          classFilesPerJavaVersion.get(targetJavaVersion).put(normalizedFileFullName, entry);
        } else {
          Integer withoutVersion = 0;
          if (!classFilesPerJavaVersion.containsKey(withoutVersion)) {
            classFilesPerJavaVersion.put(withoutVersion, new HashMap<>());
          }
          classFilesPerJavaVersion.get(withoutVersion).put(fileFullName, entry);
        }
      }
    }

    // We have to figure out what JVM version we're running on.
    Integer currentJavaVersion;
    String[] javaVersionElements =
        System.getProperty("java.version").replaceAll("\\-ea", "").split("\\.");
    if (javaVersionElements[0].equals("1")) {
      currentJavaVersion = Integer.parseInt(javaVersionElements[1]);
    } else {
      currentJavaVersion = Integer.parseInt(javaVersionElements[0]);
    }

    // Start layering the class files from old JVM version to new and thus effectively override the
    // old files by the new ones.
    Map<String, JarEntry> selectedClassFiles = new HashMap<>();
    for (Map.Entry<Integer, Map<String, JarEntry>> entry : classFilesPerJavaVersion.entrySet()) {
      Integer targetJavaVersion = entry.getKey();
      if (targetJavaVersion > currentJavaVersion) {
        break;
      }
      Map<String, JarEntry> pathToClassfile = entry.getValue();
      selectedClassFiles.putAll(pathToClassfile);
    }

    return selectedClassFiles.values();
  }