* find it when available. When this is null, use the slow way.
   */
  @J2ktIncompatible @GwtIncompatible // java.lang.reflect
  private static final @Nullable Method getStackTraceElementMethod =
      (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it

Available JDKs on your machine are automatically detected and wired for the various compile and test tasks.
Some tests require multiple JDKs to be installed on your computer, be aware of this if you make changes related to anything toolchains related.

        Class<?> optionalClass = Class.forName("java.util.Optional");
        /*
         * We don't *need* to use reflection to access Optional: It's available on all JDKs we
         * support, and Android code won't get this far, anyway, because ProcessHandle is
         * unavailable. But given how much other reflection we're using, we might as well use it

   * of Java 20, it always throws an exception, and as of Java 26, the method does not even exist.
   * For now, we continue using it to clean up under older JDKs.
   *
   * Our usages should at least be *relatively* safe: Typically, threads started by a test are dying
   * at the end of the test, so there is no object state put at risk by stopping the threads

        run: ./gradlew test allTests -Dtest.java.version=21

  testopenjdklatest:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout
        uses: actions/checkout@v6

      - name: Configure JDKs
        uses: actions/setup-java@v5
        with:
          distribution: 'zulu'
          java-version: |
            11
            17
            24

      - name: Allow incompatible JVM versions

   * of Java 20, it always throws an exception, and as of Java 26, the method does not even exist.
   * For now, we continue using it to clean up under older JDKs.
   *
   * Our usages should at least be *relatively* safe: Typically, threads started by a test are dying
   * at the end of the test, so there is no object state put at risk by stopping the threads

  // Set the Java release version.
  options.release.set(9)

  // Ignore warnings about using 'requires transitive' on automatic modules.
  // not needed when compiling with recent JDKs, e.g. 17
  options.compilerArgs.add("-Xlint:-requires-transitive-automatic")

  // Patch the compileKotlinJvm output classes into the compilation so exporting packages works correctly.
  options.compilerArgs.addAll(

            <!--
            We can apparently have only one <jdk> per execution: Others are silently ignored :(
            To properly test this, you need to remove existing toolchains:
            rm -rf ~/.m2/jdks/ ~/.m2/toolchains.xml
            (But don't run that if you have put something into ~/.m2/toolchains.xml yourself.)
            -->
            <execution>
              <id>download-25-and-surefire-version</id>

            <!--
            We can apparently have only one <jdk> per execution: Others are silently ignored :(
            To properly test this, you need to remove existing toolchains:
            rm -rf ~/.m2/jdks/ ~/.m2/toolchains.xml
            (But don't run that if you have put something into ~/.m2/toolchains.xml yourself.)
            -->
            <execution>
              <id>download-25-and-surefire-version</id>

   *       <ul>
   *         <li>UNSET, meaning "null pointer"
   *         <li>one plus an index into the entries and elements array
   *       </ul>
   *   <li>another java.util.Set delegate implementation. In most modern JDKs, normal java.util hash
   *       collections intelligently fall back to a binary search tree if hash table collisions are
   *       detected. Rather than going to all the trouble of reimplementing this ourselves, we