@Override
    public long getSpanYoungGCCollectionTime() {
        long current = getYoungGCCollectionTime();
        if (lastYoungGCCollectionTime == -1) {
            lastYoungGCCollectionTime = current;
            return 0;
        } else {
            long result = current - lastYoungGCCollectionTime;
            lastYoungGCCollectionTime = current;
            return result;
        }
    }
@author Robert HG (254963746@qq.com) on 9/15/15.
lts-core/src/main/java/com/github/ltsopensource/jvmmonitor/mbean/JVMGC.java