java 通过进程ID判断进程是否存在

在做RPA时，我知道了一个进程ID,但我想知道这个进程ID是否一直还在
经查，方法如下：

    public static boolean checkProcess(String processId) {

        boolean flag = false;
        Process process = null;
        String command = "";
        try {
            if (Platform.isWindows()) {
                command ="cmd /c tasklist  /FI \"PID eq " + processId + "\"";
            } else if (Platform.isLinux() || Platform.isAIX()) {
                command = "ps aux | awk '{print $2}'| grep -w  " + processId;
            }
            process = Runtime.getRuntime().exec(command);

            try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
                 InputStream os = process.getInputStream();) {
                byte[] b = new byte[256];
                while (os.read(b) > 0) {
                    baos.write(b);
                }
                String s = baos.toString();
                return s.contains(processId);
            }


        } catch (IOException e) {
            log.error(processId, e);
        } finally {
            if (process != null) {
                process.destroy();
            }
        }
        return flag;
    }

上述方法，无论系统是linux,还是windows,就能查到进程是否存在