How to get minor and major garbage collection count in JDK 7 and JDK 8

Question

I am trying to publish out the garbage collection statistics for my services. Few of them are running on JDK 7 and few of them on JDK8.

I have read in the question: Can you get basic GC stats in Java? that we can get the total Garbage collection count via the MBean. But I am trying to look at a slightly different picture.

I am trying to publish out the major and minor collection count separately. The above method will get the total collection count and not segregating out into minor and major.

What I have tried to do?

List<GarbageCollectorMXBean> listOfGarbageCollectionMBeans = ManagementFactory.getGarbageCollectorMXBeans();
Stats majorGCStats= null;
Stats minorGcStats = null;
for (GarbageCollectorMXBean gcMBean: listOfGarbageCollectionMBeans ) {
Stats stats = new Stats();
// in the method isMajorCollector, trying to identify if the collector is for major or minor depending on pool name
  if (isMajorCollector(gcMBean.getMemoryPoolNames())) {
    majorGCStats= stats;
  }
  else{
     minorGCStats= stats;
  }
  //Collection_MAP is a HashMap of minorGC vs Stats and majorGC vs Stats
  COLLECTION_MAP.put(stats.getName(), stats);
}

public boolean isMajorCollector(String[] poolNames){
    for (final String pool : pools) {
      if (pool.contains("Perm")|| pool.contains("Old")) {
        return true;
      }
    }
    return false;
   }
}


// An inner class to hold the time and name
class Stats{
 private String name;
 private long time;

 public void setTime(final long time){
   this.time= time;
 }

 public void setName(final String name){
   this.name=name;
 }

 public String getName(){
  return this.name;
 }

 public long getTime(){
   return this.time;
  }
 }

The collectors I get in the list are: PS Scavenge and PS MarkSweep.

For PS Scavenge the pool names are: PS Eden Space, PS Survivor Space.

For PS MarkSweep the pool names are: PS Eden Space, PS Survivor Space, PS Old Gen, PS Perm Gen

JVM parameters I am using:

-XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:+DisableExplicitGC.

No usecmsinitiatingoccupancyonly and cmsinitiatingoccupancyfraction is mentioned.

Thanks in advance.

Answer 1

 List<GarbageCollectorMXBean> gcMXBeans = ManagementFactory.getGarbageCollectorMXBeans();
 System.out.println("Minor GC count = " + gcMXBeans.get(0).getCollectionCount());
 System.out.println("Major GC count = " + gcMXBeans.get(1).getCollectionCount());

This works both for JDK 7 and JDK 8 for all typical collectors:

• -XX:+UseConcMarkSweepGC
• -XX:+UseParallelGC
• -XX:+UseSerialGC
• -XX:+UseG1GC