static boolean dumpJDK9AndNewerBootClassPath()

in toolchains/DumpPlatformClassPath.java [83:130]
33 lines of code
3 McCabe index (conditional complexity)

  static boolean dumpJDK9AndNewerBootClassPath(
      int hostMajorVersion, Path output, Path targetJavabase) throws IOException {

    // JDK 9 and newer support cross-compiling to older platform versions using the --system
    // and --release flags.
    // * --system takes the path to a JDK root for JDK 9 and up, and causes the compilation
    //     to target the APIs from that JDK.
    // * --release takes a language level (e.g. '9') and uses the API information baked in to
    //     the host JDK (in lib/ct.sym).

    // Since --system only supports JDK >= 9, first check of the target JDK defines a JDK 8
    // bootclasspath.
    List<Path> bootClassPathJars = getBootClassPathJars(targetJavabase);
    if (!bootClassPathJars.isEmpty()) {
      writeClassPathJars(output, bootClassPathJars);
      return true;
    }

    // Initialize a FileManager to process the --system argument, and then read the
    // initialized bootclasspath data back out.

    Context context = new Context();
    JavacTool.create()
        .getTask(
            /* out = */ null,
            /* fileManager = */ null,
            /* diagnosticListener = */ null,
            /* options = */ Arrays.asList("--system", String.valueOf(targetJavabase)),
            /* classes = */ null,
            /* compilationUnits = */ null,
            context);
    StandardJavaFileManager fileManager =
        (StandardJavaFileManager) context.get(JavaFileManager.class);

    SortedMap<String, InputStream> entries = new TreeMap<>();
    for (JavaFileObject fileObject :
        fileManager.list(
            StandardLocation.PLATFORM_CLASS_PATH,
            "",
            EnumSet.of(Kind.CLASS),
            /* recurse= */ true)) {
      String binaryName =
          fileManager.inferBinaryName(StandardLocation.PLATFORM_CLASS_PATH, fileObject);
      entries.put(binaryName.replace('.', '/') + ".class", fileObject.openInputStream());
    }
    writeEntries(output, entries);
    return true;
  }