Monitor GC

GCMonitor.java

import java.lang.management.GarbageCollectorMXBean;
import java.lang.management.ManagementFactory;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class GCMonitor implements Runnable {
    private final GarbageCollectorMXBean mbean;
    private long lastGCCount;
    private long lastGCTime;

    public GCMonitor(GarbageCollectorMXBean mbean) {
        this.mbean = mbean;
        this.lastGCCount = mbean.getCollectionCount();
        this.lastGCTime = mbean.getCollectionTime();
    }

    public void run() {
        long newGCCount = mbean.getCollectionCount();
        long newGCTime = mbean.getCollectionTime();
        
        if (newGCCount > lastGCCount) {
            System.out.format(
                "Full GC: count=%d, time=%dms, totalCount=%d, totalTime=%dms%n",
                newGCCount - lastGCCount, newGCTime - lastGCTime, newGCCount, newGCTime);
            lastGCCount = newGCCount;
            lastGCTime = newGCTime;
        }
    }

    private static GarbageCollectorMXBean markSweepGCBean(Iterable<GarbageCollectorMXBean> gcbeans) {
        for (GarbageCollectorMXBean gcbean : gcbeans) {
            if (gcbean.getName().indexOf("MarkSweep") >= 0) {
                return gcbean;
            }
        }
        return null;
    }

    public static void main(String[] args) throws Exception {
        long gcWait = args.length == 0 ? 100: Long.parseLong(args[0]);
        GarbageCollectorMXBean mbean = markSweepGCBean(ManagementFactory.getGarbageCollectorMXBeans());
        if (mbean == null) {
            return;
        }

        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
        scheduler.scheduleWithFixedDelay(new GCMonitor(mbean), 1, 1, TimeUnit.SECONDS);
        try {
            for (;;) {
                Thread.sleep(gcWait);
                System.gc();
            }
        } finally {
            scheduler.shutdown();
            scheduler.awaitTermination(5, TimeUnit.SECONDS);
        }
    }
}