window下:

import com.sun.management.OperatingSystemMXBean;
import java.io.File;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.lang.management.ManagementFactory;
import java.util.ArrayList;
import java.util.List;


public class windowtest {
    private static final int CPUTIME = 500;

    private static final int PERCENT = 100;

    private static final int FAULTLENGTH = 10;
    //获取cpu占用情况
    public static String getCpuRatioForWindows() {
        try {
            String procCmd = System.getenv("windir") + "\\system32\\wbem\\wmic.exe process get Caption,CommandLine,KernelModeTime,ReadOperationCount,ThreadCount,UserModeTime,WriteOperationCount";
            // 取进程信息
            long[] c0 = readCpu(Runtime.getRuntime().exec(procCmd));
            Thread.sleep(CPUTIME);
            long[] c1 = readCpu(Runtime.getRuntime().exec(procCmd));
            if (c0 != null && c1 != null) {
                long idletime = c1[0] - c0[0];
                long busytime = c1[1] - c0[1];
                return "CPU使用率:" + Double.valueOf(PERCENT * (busytime) * 1.0 / (busytime + idletime)).intValue() + "%";
            } else {
                return "CPU使用率:" + 0 + "%";
            }
        } catch (Exception ex) {
            ex.printStackTrace();
            return "CPU使用率:" + 0 + "%";
        }
    }
    private static long[] readCpu(final Process proc) {
        long[] retn = new long[2];
        try {
            proc.getOutputStream().close();
            InputStreamReader ir = new InputStreamReader(proc.getInputStream());
            LineNumberReader input = new LineNumberReader(ir);
            String line = input.readLine();
            if (line == null || line.length() < FAULTLENGTH) {
                return null;
            }
            int capidx = line.indexOf("Caption");
            int cmdidx = line.indexOf("CommandLine");
            int rocidx = line.indexOf("ReadOperationCount");
            int umtidx = line.indexOf("UserModeTime");
            int kmtidx = line.indexOf("KernelModeTime");
            int wocidx = line.indexOf("WriteOperationCount");
            long idletime = 0;
            long kneltime = 0;
            long usertime = 0;
            while ((line = input.readLine()) != null) {
                if (line.length() < wocidx) {
                    continue;
                }
                // 字段出现顺序：Caption,CommandLine,KernelModeTime,ReadOperationCount,
                // ThreadCount,UserModeTime,WriteOperation
                String caption = substring(line, capidx, cmdidx - 1).trim();
                String cmd = substring(line, cmdidx, kmtidx - 1).trim();
                if (cmd.indexOf("wmic.exe") >= 0) {
                    continue;
                }
                String s1 = substring(line, kmtidx, rocidx - 1).trim();
                String s2 = substring(line, umtidx, wocidx - 1).trim();
                if (caption.equals("System Idle Process") || caption.equals("System")) {
                    if (s1.length() > 0)
                        idletime += Long.valueOf(s1).longValue();
                    if (s2.length() > 0)
                        idletime += Long.valueOf(s2).longValue();
                    continue;
                }
                if (s1.length() > 0)
                    kneltime += Long.valueOf(s1).longValue();
                if (s2.length() > 0)
                    usertime += Long.valueOf(s2).longValue();
            }
            retn[0] = idletime;
            retn[1] = kneltime + usertime;
            return retn;
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                proc.getInputStream().close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return null;
    }
    /**
     * 由于String.subString对汉字处理存在问题（把一个汉字视为一个字节)，因此在 包含汉字的字符串时存在隐患，现调整如下：
     *
     * @param src       要截取的字符串
     * @param start_idx 开始坐标（包括该坐标)
     * @param end_idx   截止坐标（包括该坐标）
     * @return java.lang.String
     * @author loulan
     */
    private static String substring(String src, int start_idx, int end_idx) {
        byte[] b = src.getBytes();
        String tgt = "";
        for (int i = start_idx; i <= end_idx; i++) {
            tgt += (char) b[i];
        }
        return tgt;
    }
    /**
     * 获取内存使用率
     *
     * @return java.lang.String
     * @author loulan
     */
    public static String getMemery() {
        // 用管理工厂获取操作系统属性
        OperatingSystemMXBean operatingSystemMXBean = (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
        // 总的物理内存+虚拟内存
        long totalvirtualMemory = operatingSystemMXBean.getTotalSwapSpaceSize();
        // 剩余的物理内存
        long freePhysicalMemorySize = operatingSystemMXBean.getFreePhysicalMemorySize();
        Double compare = (Double) (1 - freePhysicalMemorySize * 1.0 / totalvirtualMemory) * 100;
        return "内存已使用:" + compare.intValue() + "%";
    }

    /**
     * 获取文件系统使用率
     *
     * @return java.util.List<java.lang.String>
     * @author loulan
     */
    public static List<String> getDisk() {
        // 操作系统
        List<String> list = new ArrayList<String>();
        for (char c = 'A'; c <= 'Z'; c++) {
            String dirName = c + ":/";
            File win = new File(dirName);
            if (win.exists()) {
                long total = (long) win.getTotalSpace();
                long free = (long) win.getFreeSpace();
                Double compare = (Double) (1 - free * 1.0 / total) * 100;
                String str = c + ":盘  已使用 " + compare.intValue() + "%";
                list.add(str);
            }
        }
        return list;
    }
    public static void main(String[] args) {
       List<String> a=windowtest.getDisk();
       a.forEach(zhi-> System.out.println(zhi));
    }
}

linux下:

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.util.*;
public class linuxtest {
    /**
     * 获取磁盘使用率
     *
     * @return int
     * @author loulan
     */
    public static int getDiskUsage() throws Exception {
        double totalHD = 0;
        double usedHD = 0;
        Runtime rt = Runtime.getRuntime();
        // df -hl 查看硬盘空间
        Process p = rt.exec("df -hl");
        BufferedReader in = null;
        try {
            in = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String str = null;
            String[] strArray = null;
            while ((str = in.readLine()) != null) {
                int m = 0;
                strArray = str.split(" ");
                for (String tmp : strArray) {
                    if (tmp.trim().length() == 0)
                        continue;
                    ++m;
                    if (tmp.indexOf("G") != -1) {
                        if (m == 2) {
                            if (!tmp.equals("") && !tmp.equals("0"))
                                totalHD += Double.parseDouble(tmp.substring(0, tmp.length() - 1)) * 1024;
                        }
                        if (m == 3) {
                            if (!tmp.equals("none") && !tmp.equals("0"))
                                usedHD += Double.parseDouble(tmp.substring(0, tmp.length() - 1)) * 1024;
                        }
                    }
                    if (tmp.indexOf("M") != -1) {
                        if (m == 2) {
                            if (!tmp.equals("") && !tmp.equals("0"))
                                totalHD += Double.parseDouble(tmp.substring(0, tmp.length() - 1));
                        }
                        if (m == 3) {
                            if (!tmp.equals("none") && !tmp.equals("0"))
                                usedHD += Double.parseDouble(tmp.substring(0, tmp.length() - 1));
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.getStackTrace();
        } finally {
            in.close();
        }
        // 保留2位小数
        double precent = (usedHD / totalHD) * 100;
        BigDecimal b1 = new BigDecimal(precent);
        precent = b1.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();
        return (int) precent;
    }

    /**
     * 获取cpu使用率
     *
     * @return int
     * @author loulan
     */
    public static int getCpuUsage() {
        try {
            Map<?, ?> map1 = linuxtest.getCpuinfo();
            Thread.sleep(5 * 1000);
            Map<?, ?> map2 = linuxtest.getCpuinfo();

            long user1 = Long.parseLong(map1.get("user").toString());
            long nice1 = Long.parseLong(map1.get("nice").toString());
            long system1 = Long.parseLong(map1.get("system").toString());
            long idle1 = Long.parseLong(map1.get("idle").toString());

            long user2 = Long.parseLong(map2.get("user").toString());
            long nice2 = Long.parseLong(map2.get("nice").toString());
            long system2 = Long.parseLong(map2.get("system").toString());
            long idle2 = Long.parseLong(map2.get("idle").toString());

            long total1 = user1 + system1 + nice1;
            long total2 = user2 + system2 + nice2;
            float total = total2 - total1;

            long totalIdle1 = user1 + nice1 + system1 + idle1;
            long totalIdle2 = user2 + nice2 + system2 + idle2;
            float totalidle = totalIdle2 - totalIdle1;

            float cpusage = (total / totalidle) * 100;
            return (int) cpusage;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return 0;
    }


    /**
     * 获取CPU使用信息
     *
     * @return java.util.Map
     * @author loulan
     */
    public static Map<?, ?> getCpuinfo() {
        InputStreamReader inputs = null;
        BufferedReader buffer = null;
        Map<String, Object> map = new HashMap<String, Object>();
        try {
            inputs = new InputStreamReader(new FileInputStream("/proc/stat"));
            buffer = new BufferedReader(inputs);
            String line = "";
            while (true) {
                line = buffer.readLine();
                if (line == null) {
                    break;
                }
                if (line.startsWith("cpu")) {
                    StringTokenizer tokenizer = new StringTokenizer(line);
                    List<String> temp = new ArrayList<String>();
                    while (tokenizer.hasMoreElements()) {
                        String value = tokenizer.nextToken();
                        temp.add(value);
                    }
                    map.put("user", temp.get(1));
                    map.put("nice", temp.get(2));
                    map.put("system", temp.get(3));
                    map.put("idle", temp.get(4));
                    map.put("iowait", temp.get(5));
                    map.put("irq", temp.get(6));
                    map.put("softirq", temp.get(7));
                    map.put("stealstolen", temp.get(8));
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                buffer.close();
                inputs.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return map;
    }


    /**
     * 获取内存使用率
     *
     * @return int
     * @author loulan
     */
    public static int getMemoryUsage() {
        Map<String, Object> map = new HashMap<String, Object>();
        InputStreamReader inputs = null;
        BufferedReader buffer = null;
        try {
            inputs = new InputStreamReader(new FileInputStream("/proc/meminfo"));
            buffer = new BufferedReader(inputs);
            String line = "";
            while (true) {
                line = buffer.readLine();
                if (line == null)
                    break;
                int beginIndex = 0;
                int endIndex = line.indexOf(":");
                if (endIndex != -1) {
                    String key = line.substring(beginIndex, endIndex);
                    beginIndex = endIndex + 1;
                    endIndex = line.length();
                    String memory = line.substring(beginIndex, endIndex);
                    String value = memory.replace("kB", "").trim();
                    map.put(key, value);
                }
            }

            long memTotal = Long.parseLong(map.get("MemTotal").toString());
            long memFree = Long.parseLong(map.get("MemFree").toString());
            long memused = memTotal - memFree;
            long buffers = Long.parseLong(map.get("Buffers").toString());
            long cached = Long.parseLong(map.get("Cached").toString());

            double usage = (double) (memused - buffers - cached) / memTotal * 100;
            return (int) usage;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                buffer.close();
                inputs.close();
            } catch (Exception e2) {
                e2.printStackTrace();
            }
        }
        return 0;
    }
}