ParallelExecutor.java

import java.util.Arrays;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class ParallelExecutor {

  public static void main(String[] args) {
    int nThreads = Integer.parseInt(args[0]);
    if (nThreads <= 0) {
      nThreads = Runtime.getRuntime().availableProcessors();
    }

    ExecutorService threadPool = Executors.newFixedThreadPool(nThreads);
    Stream<String> commands =
        args.length > 1
            ? Arrays.stream(args).skip(1)
            : new Scanner(System.in).useDelimiter(System.lineSeparator()).tokens();

    try {
      commands
          .map(
              command ->
                  threadPool.submit(
                      () ->
                          new ProcessBuilder("cmd.exe", "/c", command)
                              .inheritIO()
                              .start()
                              .waitFor()))
          .collect(Collectors.toList())
          .forEach(
              it -> {
                try {
                  it.get();
                } catch (Exception e) {
                  throw new RuntimeException(e);
                }
              });
    } finally {
      threadPool.shutdownNow();
    }
  }
}