GarbageCollectorInfo.java

import com.sun.management.GcInfo;
import javax.management.MBeanServer;
import java.io.IOException;
import java.lang.management.ManagementFactory;
import com.sun.management.GarbageCollectorMXBean;
import java.lang.management.MemoryUsage;
import java.util.Map;
import java.util.Random;
import java.util.concurrent.Executors;

import static java.util.concurrent.TimeUnit.SECONDS;

class GarbageCollectorInfo {
    static final String YGEN_COLLECTOR_NAME = "java.lang:type=GarbageCollector,name=ParNew";
    static final String OGEN_COLLECTOR_NAME = "java.lang:type=GarbageCollector,name=ConcurrentMarkSweep";

    static final GarbageCollectorMXBean ygenMBean;
    static final GarbageCollectorMXBean ogenMBean;

    static {
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();

        GarbageCollectorMXBean mBean = null;
        try {
            mBean = ManagementFactory.newPlatformMXBeanProxy(server, YGEN_COLLECTOR_NAME, GarbageCollectorMXBean.class);
        } catch (IOException e) {
            e.printStackTrace();
        }
        ygenMBean = mBean;

        try {
            mBean = ManagementFactory.newPlatformMXBeanProxy(server, OGEN_COLLECTOR_NAME, GarbageCollectorMXBean.class);
        } catch (IOException e) {
            e.printStackTrace();
        }
        ogenMBean = mBean;
    }


    private long lastYGId;
    private long lastOGId;

    public void printYGenCollectionStats() {
        lastYGId = printCollectionStats(ygenMBean, lastYGId, false);
    }

    public void printOGenCollectionStats() {
        lastOGId = printCollectionStats(ogenMBean, lastOGId, true);
    }

    private static long printCollectionStats(GarbageCollectorMXBean mBean, Long lastId, boolean isOldGen) {
        GcInfo info = mBean.getLastGcInfo();
        if (info == null) {
            return lastId;
        }

        long id = info.getId();
        if (id == lastId) {
            return lastId;
        }

        long start = info.getStartTime();
        long end = info.getEndTime();
        if (start == end) {
            return lastId;
        }

        System.out.printf("Duration of '%s' collection %d was %d ms.\n", mBean.getName(), id, end - start);

        Map<String, MemoryUsage> before = info.getMemoryUsageBeforeGc();
        Map<String, MemoryUsage> after = info.getMemoryUsageAfterGc();

        MemoryUsage survivorBefore = before.get("Par Survivor Space");
        MemoryUsage edenBefore = before.get("Par Eden Space");
        MemoryUsage oldGenBefore = before.get("CMS Old Gen");

        MemoryUsage survivorAfter = after.get("Par Survivor Space");
        MemoryUsage edenAfter = after.get("Par Eden Space");
        MemoryUsage oldGenAfter = after.get("CMS Old Gen");


        long deltaSize = isOldGen ? oldGenBefore.getUsed() - oldGenAfter.getUsed()
                                  : edenBefore.getUsed() - edenAfter.getUsed();

        deltaSize /= 1024 * 1024;
        System.out.printf("Cleaned up a total of %d MB.\n", deltaSize);

        return id;
    }
}

public class Main {

    static {
        Executors.newScheduledThreadPool(1).scheduleAtFixedRate(new Runnable() {

            GarbageCollectorInfo info = new GarbageCollectorInfo();

            @Override
            public void run() {
                info.printYGenCollectionStats();
                info.printOGenCollectionStats();
            }
        }, 0, 1, SECONDS);
    }

    public static void main(String[] args) throws InterruptedException {

        byte[][] bytes = new byte[51200][];
        Random rand = new Random();
        for (long i = 0; i < 100000000000l; i++) {
            byte[] bytes0 = new byte[1024];
            rand.nextBytes(bytes0);
            bytes[(int) (i % bytes.length)] = bytes0;
        }

        System.out.println("done" + bytes.length);

    }
}

Example output:

/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/bin/java -XX:+UseConcMarkSweepGC -Xms200m -Xmx200m -XX:NewSize=50m -XX:MaxNewSize=50m -Didea.launcher.port=7536 "-Didea.launcher.bin.path=/Applications/IntelliJ IDEA 14 CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/lib/tools.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Users/jakobbuchgraber/Code/beantest/out/production/bean:/Applications/IntelliJ IDEA 14 CE.app/Contents/lib/idea_rt.jar" com.intellij.rt.execution.application.AppMain Main
Duration of 'ParNew' collection 4 was 17 ms.
Cleaned up a total of 40 MB.
Duration of 'ConcurrentMarkSweep' collection 2 was 17 ms.
Cleaned up a total of 36 MB.
Duration of 'ParNew' collection 11 was 13 ms.
Cleaned up a total of 40 MB.
Duration of 'ConcurrentMarkSweep' collection 8 was 120 ms.
Cleaned up a total of 34 MB.
Duration of 'ParNew' collection 17 was 14 ms.
Cleaned up a total of 40 MB.
Duration of 'ConcurrentMarkSweep' collection 15 was 123 ms.
Cleaned up a total of 35 MB.
...