The following is an example of the ExecutorService to make system calls.

CmdTdev.java

package dev.sysadmin.test;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class CmdTdev {
  private static int myid;

	public CmdTdev() {
		myid++;
	}

	public void perform() {
		System.out.println("id " + myid + " start sleep");
		new Sleep(5);
		System.out.println("id " + myid + " after sleep");

	}

	public static void main(String[] args) {

		CmdTdev c = new CmdTdev();

		int scaleFactor = 2;

		int cpus = Runtime.getRuntime().availableProcessors();
		int maxThreads = cpus * scaleFactor;
		maxThreads = (maxThreads > 0 ? maxThreads : 1);
		System.out.println("cpus: " + cpus);
		System.out.println("maxThreads: " + maxThreads);

		ExecutorService executorService = new ThreadPoolExecutor(maxThreads, // core
																				// thread
																				// pool
																				// size
				maxThreads, // maximum thread pool size
				1, // time to wait before resizing pool
				TimeUnit.MINUTES, new ArrayBlockingQueue<Runnable>(maxThreads,
						true), new ThreadPoolExecutor.CallerRunsPolicy());

		for (int i = 0; i < 5; ++i) {
			executorService.submit(new Runnable() {
				@Override
				public void run() {
					try {
						// if it's a file, process it
						new CmdW().perform(new String[] { "imac","rh","rh2","ss","tv","pi" });
					} catch (Exception ex) {
						// error management logic
					}
				}
			});
		}

		executorService.shutdown();

		try {
			if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
				// pool didn't terminate after the first try
				executorService.shutdownNow();
			}

			if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
				// pool didn't terminate after the second try
			}
		} catch (InterruptedException ex) {
			executorService.shutdownNow();
			Thread.currentThread().interrupt();
		}

	}

}

CmdW.java

package dev.sysadmin.test;

/*
 *          String s = "ps -ef "+i+"|grep 'RSite:'|sort";
 CmdW cmd = new CmdW(new String[] { "/bin/bash","-c",s, });
 * 
 * 
 */

import java.util.*;
import java.io.*;

class StrGrab0 extends Thread {
	private InputStream is;
	private String type;
	private List<String> lines = new ArrayList<String>();
	private Collection<String> c = Collections.synchronizedCollection(lines);
	private String delims = new String("[ ,\t]+");

	StrGrab0(InputStream is, String type) {
		this.is = is;
		this.type = type;

	}

	public void pr() {

		synchronized (c) {
			Iterator<String> i = c.iterator();
			while (i.hasNext()) {
				System.out.println(i.next());
			}
		}

	}

	public void clear() {
		lines.clear();
	}

	public List<String> getList() {
		return lines;
	}

	public void setDelims(String delims) {
		this.delims = delims;
	}

	public String[][] getTokens() {

		Object[] data = lines.toArray();
		// String delims = "[ ,\t]+";
		String[][] tokens;
		tokens = new String[data.length][];
		for (int i = 0; i < data.length; ++i) {
			tokens[i] = data[i].toString().split(delims);
		}
		return tokens;
	}

	public void run() {
		try {
			InputStreamReader isr = new InputStreamReader(is);
			BufferedReader br = new BufferedReader(isr);
			String line = null;

			synchronized (c) {
				while ((line = br.readLine()) != null) {
					c.add(line.toString());
				}
			}
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}
	}
}

public class CmdW {
	// Process proc = rt.exec(new String[]
	// {"ssh","rh","df","-h","|","grep","-v","'^Filesystem'","|","awk '{print $5,$6}'"});

	private StrGrab0 errorGrab;
	private StrGrab0 outputGrab;
	private int exitVal;
	private String osName;

	public CmdW() {

	}

	CmdW(String[] cmd) {

		try {
			osName = System.getProperty("os.name");
			// System.out.println("System: "+osName);
			Runtime rt = Runtime.getRuntime();
			Process proc = rt.exec(cmd);
			this.errorGrab = new StrGrab0(proc.getErrorStream(), "ERROR");
			this.outputGrab = new StrGrab0(proc.getInputStream(), "OUTPUT");

			// kick them off
			this.errorGrab.start();
			this.outputGrab.start();

			// any error???
			this.exitVal = proc.waitFor();

			// System.out.println("ExitValue: " + exitVal);
		} catch (Throwable t) {
			t.printStackTrace();
		}

	}

	public void pr() {
		outputGrab.pr();
	}

	public String[][] getTokens() {
		return outputGrab.getTokens();
	}

	public void setDelims(String delims) {
		outputGrab.setDelims(delims);
	}

	public void prE() {
		errorGrab.pr();
	}

	public void perform(String[] servers) {
		for (String i : servers) {
			System.out.println("\nServer:" + i);
			String scmd = "date >> /tmp/CmdW";
			CmdW c = new CmdW(new String[] { "/usr/bin/ssh", "-q", "-o",
					"ConnectTimeout=1", "-o", "NumberOfPasswordPrompts=0", i,
					scmd });
			c.pr();
			String[][] s = c.getTokens();
			if (s.length >= 1) {
				System.out.println(s.length);
				if (s[1].length >= 1) {
					System.out.println(s[1].length);
					System.out.println(s[1][1]);
				}
			}
		}
	}

	public static void main(String args[]) {

		for (String i : new String[] { "mAW" }) {
			System.out.println("\nServer:" + i);
			String scmd = "date  >> /tmp/CmdW";
			CmdW c = new CmdW(new String[] { "/usr/bin/ssh", "-q", "-o",
					"ConnectTimeout=1", "-o", "NumberOfPasswordPrompts=0", i,
					scmd });
			c.pr();
			String[][] s = c.getTokens();
			if (s.length >= 0) {
				System.out.println(s.length);

			}
		}

	}
}