code: package io.ray.runtime.util;
  
  import java.io.IOException;
  import java.lang.management.ManagementFactory;
  import java.lang.management.RuntimeMXBean;
  import java.util.concurrent.locks.ReentrantLock;
  
  /** some utilities for system process. */
  public class SystemUtil {
  
    static final ReentrantLock pidlock = new ReentrantLock();
    static Integer pid;
  
    public static int pid() {
      if (pid == null) {
        pidlock.lock();
        try {
          if (pid == null) {
            RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();
            String name = runtime.getName();
            int index = name.indexOf("@");
            if (index != -1) {
              pid = Integer.parseInt(name.substring(0, index));
            } else {
              throw new RuntimeException("parse pid error:" + name);
            }
          }
  
        } finally {
          pidlock.unlock();
        }
      }
      return pid;
    }
  
    public static boolean isProcessAlive(int pid) {
      Process process;
      try {
        process = Runtime.getRuntime().exec(new String[] {"kill", "-0", String.valueOf(pid)});
        process.waitFor();
      } catch (InterruptedException | IOException e) {
        throw new RuntimeException(e);
      }
      return process.exitValue() == 0;
    }
  }
  