@Override
    public long getSpanFullGCCollectionTime() {
        long current = getFullGCCollectionTime();
        if (lastFullGCCollectionTime == -1) {
            lastFullGCCollectionTime = current;
            return 0;
        } else {
            long result = current - lastFullGCCollectionTime;
            lastFullGCCollectionTime = 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