回答我自己的问题；我写了一些代码…

网络数据：

public class NetworkData {

    static Map<String, Long> rxCurrentMap = new HashMap<String, Long>();
    static Map<String, List<Long>> rxChangeMap = new HashMap<String, List<Long>>();
    static Map<String, Long> txCurrentMap = new HashMap<String, Long>();
    static Map<String, List<Long>> txChangeMap = new HashMap<String, List<Long>>();
    private static Sigar sigar;

    /**
     * @throws InterruptedException
     * @throws SigarException
     * 
     */
    public NetworkData(Sigar s) throws SigarException, InterruptedException {
        sigar = s;
        getMetric();
        System.out.println(networkInfo());
        Thread.sleep(1000);     
    }

    public static void main(String[] args) throws SigarException,
            InterruptedException {
        new NetworkData(new Sigar());
        NetworkData.startMetricTest();
    }

    public static String networkInfo() throws SigarException {
        String info = sigar.getNetInfo().toString();
        info += "\n"+ sigar.getNetInterfaceConfig().toString();
        return info;
    }

    public static String getDefaultGateway() throws SigarException {
        return sigar.getNetInfo().getDefaultGateway();
    }

    public static void startMetricTest() throws SigarException, InterruptedException {
        while (true) {
            Long[] m = getMetric();
            long totalrx = m[0];
            long totaltx = m[1];
            System.out.print("totalrx(download): ");
            System.out.println("\t" + Sigar.formatSize(totalrx));
            System.out.print("totaltx(upload): ");
            System.out.println("\t" + Sigar.formatSize(totaltx));
            System.out.println("-----------------------------------");
            Thread.sleep(1000);
        }

    }

    public static Long[] getMetric() throws SigarException {
        for (String ni : sigar.getNetInterfaceList()) {
            // System.out.println(ni);
            NetInterfaceStat netStat = sigar.getNetInterfaceStat(ni);
            NetInterfaceConfig ifConfig = sigar.getNetInterfaceConfig(ni);
            String hwaddr = null;
            if (!NetFlags.NULL_HWADDR.equals(ifConfig.getHwaddr())) {
                hwaddr = ifConfig.getHwaddr();
            }
            if (hwaddr != null) {
                long rxCurrenttmp = netStat.getRxBytes();
                saveChange(rxCurrentMap, rxChangeMap, hwaddr, rxCurrenttmp, ni);
                long txCurrenttmp = netStat.getTxBytes();
                saveChange(txCurrentMap, txChangeMap, hwaddr, txCurrenttmp, ni);
            }
        }
        long totalrxDown = getMetricData(rxChangeMap);
        long totaltxUp = getMetricData(txChangeMap);
        for (List<Long> l : rxChangeMap.values())
            l.clear();
        for (List<Long> l : txChangeMap.values())
            l.clear();
        return new Long[] { totalrxDown, totaltxUp };
    }

    private static long getMetricData(Map<String, List<Long>> rxChangeMap) {
        long total = 0;
        for (Entry<String, List<Long>> entry : rxChangeMap.entrySet()) {
            int average = 0;
            for (Long l : entry.getValue()) {
                average += l;
            }
            total += average / entry.getValue().size();
        }
        return total;
    }

    private static void saveChange(Map<String, Long> currentMap,
            Map<String, List<Long>> changeMap, String hwaddr, long current,
            String ni) {
        Long oldCurrent = currentMap.get(ni);
        if (oldCurrent != null) {
            List<Long> list = changeMap.get(hwaddr);
            if (list == null) {
                list = new LinkedList<Long>();
                changeMap.put(hwaddr, list);
            }
            list.add((current - oldCurrent));
        }
        currentMap.put(ni, current);
    }

}

CPU数据：

public class CpuData {
    private static Sigar sigar;

    public CpuData(Sigar s) throws SigarException {
        sigar = s;
        System.out.println(cpuInfo());
    }

    public static void main(String[] args) throws InterruptedException, SigarException {
        new CpuData(new Sigar());
        CpuData.startMetricTest();
    }

    private static void startMetricTest() throws InterruptedException, SigarException {
        new Thread() {
            public void run() {
                while(true) 
                BigInteger.probablePrime(MAX_PRIORITY, new Random());
            };
        }.start();
        while(true) {
            String pid = ""+sigar.getPid();
            System.out.print(getMetric(pid));
            for(Double d:getMetric()){
                System.out.print("\t"+d);
            }
            System.out.println();
            Thread.sleep(1000);
        }       
    }

    public String cpuInfo() throws SigarException {
        CpuInfo[] infos = sigar.getCpuInfoList();
        CpuInfo info = infos[0];

        String infoString = info.toString();
        if ((info.getTotalCores() != info.getTotalSockets())
                || (info.getCoresPerSocket() > info.getTotalCores())) {
            infoString+=" Physical CPUs: " + info.getTotalSockets();
            infoString+=" Cores per CPU: " + info.getCoresPerSocket();
        }

        long cacheSize = info.getCacheSize();
        if (cacheSize != Sigar.FIELD_NOTIMPL) {
            infoString+="Cache size...." + cacheSize;
        }
        return infoString;
    }

    public static Double[] getMetric() throws SigarException {
        CpuPerc cpu = sigar.getCpuPerc();
        double system = cpu.getSys();
        double user = cpu.getUser();
        double idle = cpu.getIdle();
//      System.out.println("idle: " +CpuPerc.format(idle) +", system: "+CpuPerc.format(system)+ ", user: "+CpuPerc.format(user));
        return new Double[] {system, user, idle};
    }

    public static double getMetric(String pid) throws SigarException {
        ProcCpu cpu = sigar.getProcCpu(pid);
//      System.out.println(sigar.getProcFd(pid));
//      System.err.println(cpu.toString());
        return cpu.getPercent();
    }

}

RAM数据：

public class RamData {

    private static Sigar sigar;
    private static Map<String, Long> pageFoults;

    public RamData(Sigar s) throws SigarException {
        sigar = s;
        System.out.println(getMetric().toString());
    }

    public static void main(String[] args) throws SigarException,
            InterruptedException {
        new RamData(new Sigar());
        RamData.startMetricTest();
    }

    public static void startMetricTest() throws SigarException,
            InterruptedException {
        while (true) {
            Map<String, String> map = RamData.getMetric("" + sigar.getPid());
            System.out.println("Resident: \t\t"
                    + Sigar.formatSize(Long.valueOf(map.get("Resident"))));
            System.out.println("PageFaults: \t\t" + map.get("PageFaults"));
            System.out.println("PageFaultsTotal:\t" + map.get("PageFaultsTotal"));
            System.out.println("Size:    \t\t"
                    + Sigar.formatSize(Long.valueOf(map.get("Size"))));
            Map<String, String> map2 = getMetric();
            for (Entry<String, String> e : map2.entrySet()) {
                String s;
                try {
                    s = Sigar.formatSize(Long.valueOf(e.getValue()));
                } catch (NumberFormatException ex) {
                    s = ((int) (double) Double.valueOf(e.getValue())) + "%";
                }
                System.out.print("  " + e.getKey() + ": " + s);
            }
            System.out.println("\n------------------");
            Thread.sleep(1000);
        }
    }

    public static Map<String, String> getMetric() throws SigarException {
        Mem mem = sigar.getMem();
        return (Map<String, String>) mem.toMap();
    }

    public static Map<String, String> getMetric(String pid)
            throws SigarException {
        if (pageFoults == null)
            pageFoults = new HashMap<String, Long>();
        ProcMem state = sigar.getProcMem(pid);
        Map<String, String> map = new TreeMap<String, String>(state.toMap());
        if (!pageFoults.containsKey(pid))
            pageFoults.put(pid, state.getPageFaults());
        map.put("PageFaults", ""
                + (state.getPageFaults() - pageFoults.get(pid)));
        map.put("PageFaultsTotal", ""+state.getPageFaults());
        return map;
    }
}

过程数据：

public class ProcessData {

    private static Sigar sigar;

    public ProcessData(Sigar s) throws SigarException {
        this.sigar = s;
        System.out.println(getMetric().toString());
        System.out.println(getMetric(getPidString()).toString());
    }

    public static void main(String[] args) throws SigarException {
        new ProcessData(new Sigar());
        System.out.println(ProcessData.getMetric());
        System.out.println(ProcessData.getMetric(getPidString()));
    }

    public static Map<String, String> getMetric() throws SigarException {
        ProcStat state = sigar.getProcStat();
        return (Map<String, String>) state.toMap();
    }

    public static Map<String, String> getMetric(String pid) throws SigarException {
        ProcState state = sigar.getProcState(pid);
        return (Map<String, String>) state.toMap();
    }

    public static long getPid() {
        return sigar.getPid();
    }

    public static String getPidString() {
        return ""+sigar.getPid();
    }

}