ThreadPoolSupport implements AutoCloseable { @Override public String toString() { return concurrentExecutor.toString(); } ThreadPoolSupport(); static ThreadPoolSupport getInstance(); @Override void close(); Executor getExecutor(); CompletableFuture<T> newCompletableFuture(Supplier<T> computation); List<Future<T>> invokeAll(
            final ThreadPoolExecutionMode proposedExecutionMode,
            @Nullable final List<? extends Callable<T>> callables); List<Future<T>> invokeAll(@Nullable final List<? extends Callable<T>> callables); List<?> join(@Nullable final List<? extends Future<?>> futures); List<T> joinGatherFailures(final List<? extends Future<T>> futures); T join(final Future<T> future); @Override String toString(); static ThreadPoolExecutionMode HIGHEST_CONCURRENCY_EXECUTION_MODE_ALLOWED; }
@Test void shouldPreserveSequence_whenNoThread() { buffer.append("A"); buffer.append("B"); buffer.append("C"); Assertions.assertEquals("ABC", buffer.toString()); }