如何以编程方式获取 GC 类直方图

Question

我想以编程方式获得以下命令的相同结果：

jcmd <pid> GC.class_histogram | grep 'sun.util'

 728:            27           2592  sun.util.calendar.Gregorian$Date
 800:            44           2112  sun.util.locale.LocaleObjectCache$CacheEntry
 816:            36           2016  sun.util.calendar.ZoneInfo
1169:            22            880  sun.util.locale.BaseLocale$Key

...

我已经搜索了很多答案，但没有找到明确的答案并做我想做的事，有什么办法可以做到这一点吗？

Answer 1

下面的代码显示了相同的结果：

import javax.management.MBeanException;
import javax.management.ReflectionException;

import com.sun.management.DiagnosticCommandMBean;

import sun.management.ManagementFactoryHelper;

@SuppressWarnings("restriction")
public class ClassHistogram {

    public static void main(String[] args) throws MBeanException, ReflectionException {
        DiagnosticCommandMBean dcmd = ManagementFactoryHelper.getDiagnosticCommandMBean();

        String[] emptyStringArgs = {};
        Object[] dcmdArgs = { emptyStringArgs };
        String[] signature = { String[].class.getName() };
        System.out.println(dcmd.invoke("gcClassHistogram", dcmdArgs, signature));
    }

}

可用命令的参考：https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/tooldescr006.html