我想获得总物理内存、CPU使用情况以及正在使用的内存量。我已经研究了Runtime.freeMemory()，但这并不是整个系统的空闲内存。
我知道我的答案迟到了，但我觉得这段代码很有趣。这是对"封闭"代码的改编，在直接应用之前应该进行修改：
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.lang.Process;
import java.lang.Runtime;
import java.util.HashMap;
/**
* SystemStatusReader is a collection of methods to read system status (cpu and memory)
*
* @author Andreu Correa Casablanca
*/
public class SystemStatusReader
{
public static final int CONSERVATIVE = 0;
public static final int AVERAGE = 1;
public static final int OPTIMISTIC = 2;
/**
* cpuUsage gives us the percentage of cpu usage
*
* mpstat -P ALL out stream example:
*
* Linux 3.2.0-30-generic (castarco-laptop) 10/09/12 _x86_64_ (2 CPU) - To discard
* - To discard
* 00:16:30 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle - To discard
* 00:16:30 all 17,62 0,03 3,55 0,84 0,00 0,03 0,00 0,00 77,93
* 00:16:30 0 17,36 0,05 3,61 0,83 0,00 0,05 0,00 0,00 78,12
* 00:16:30 1 17,88 0,02 3,49 0,86 0,00 0,01 0,00 0,00 77,74
*
* @param measureMode Indicates if we want optimistic, convervative or average measurements.
*/
public static Double cpuUsage (int measureMode) throws Exception {
BufferedReader mpstatReader = null;
String mpstatLine;
String[] mpstatChunkedLine;
Double selected_idle;
try {
Runtime runtime = Runtime.getRuntime();
Process mpstatProcess = runtime.exec("mpstat -P ALL");
mpstatReader = new BufferedReader(new InputStreamReader(mpstatProcess.getInputStream()));
// We discard the three first lines
mpstatReader.readLine();
mpstatReader.readLine();
mpstatReader.readLine();
mpstatLine = mpstatReader.readLine();
if (mpstatLine == null) {
throw new Exception("mpstat didn't work well");
} else if (measureMode == SystemStatusReader.AVERAGE) {
mpstatChunkedLine = mpstatLine.replaceAll(",", ".").split("\s+");
selected_idle = Double.parseDouble(mpstatChunkedLine[10]);
} else {
selected_idle = (measureMode == SystemStatusReader.CONSERVATIVE)?200.:0.;
Double candidate_idle;
int i = 0;
while((mpstatLine = mpstatReader.readLine()) != null) {
mpstatChunkedLine = mpstatLine.replaceAll(",", ".").split("\s+");
candidate_idle = Double.parseDouble(mpstatChunkedLine[10]);
if (measureMode == SystemStatusReader.CONSERVATIVE) {
selected_idle = (selected_idle < candidate_idle)?selected_idle:candidate_idle;
} else if (measureMode == SystemStatusReader.OPTIMISTIC) {
selected_idle = (selected_idle > candidate_idle)?selected_idle:candidate_idle;
}
++i;
}
if (i == 0) {
throw new Exception("mpstat didn't work well");
}
}
} catch (Exception e) {
throw e; // It's not desirable to handle the exception here
} finally {
if (mpstatReader != null) try {
mpstatReader.close();
} catch (IOException e) {
// Do nothing
}
}
return 100-selected_idle;
}
/**
* memoryUsage gives us data about memory usage (RAM and SWAP)
*/
public static HashMap<String, Integer> memoryUsage () throws Exception {
BufferedReader freeReader = null;
String freeLine;
String[] freeChunkedLine;
HashMap<String, Integer> usageData = new HashMap<String, Integer>();
try {
Runtime runtime = Runtime.getRuntime();
Process freeProcess = runtime.exec("free -k"); // We measure memory in kilobytes to obtain a greater granularity
freeReader = new BufferedReader(new InputStreamReader(freeProcess.getInputStream()));
// We discard the first line
freeReader.readLine();
freeLine = freeReader.readLine();
if (freeLine == null) {
throw new Exception("free didn't work well");
}
freeChunkedLine = freeLine.split("\s+");
usageData.put("total", Integer.parseInt(freeChunkedLine[1]));
freeLine = freeReader.readLine();
if (freeLine == null) {
throw new Exception("free didn't work well");
}
freeChunkedLine = freeLine.split("\s+");
usageData.put("used", Integer.parseInt(freeChunkedLine[2]));
freeLine = freeReader.readLine();
if (freeLine == null) {
throw new Exception("free didn't work well");
}
freeChunkedLine = freeLine.split("\s+");
usageData.put("swap_total", Integer.parseInt(freeChunkedLine[1]));
usageData.put("swap_used", Integer.parseInt(freeChunkedLine[2]));
} catch (Exception e) {
throw e;
} finally {
if (freeReader != null) try {
freeReader.close();
} catch (IOException e) {
// Do nothing
}
}
return usageData;
}
}
您可以使用SIGAR(http://support.hyperic.com/display/SIGAR/Home)。我相信这是跨平台的（我只在Windows上尝试过），我知道它有效（因为我已经尝试过）。
Javadoc：http://www.hyperic.com/support/docs/sigar/
二进制文件：http://support.hyperic.com/display/SIGAR/Home#Home-二进制
内存和CPU
CPU示例：
static final ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
...
long start = threadBean.getCurrentThreadCpuTime();
for (int i = 0; i < 10000000; i++) {
...
}
long finish = threadBean.getCurrentThreadCpuTime();
在Linux上，您可以将/proc/meminfo作为文本文件打开并解析结果。
通过'jconsole'使用JMX，如果这是交互式使用的话。它显示了很好的实时图形和许多其他诊断信息。