Date createTime.clone

public Date getCreateTime() {
        if(null == createTime) {
            return null;
        }
        return (Date) createTime.clone();
    }

    public void setCreateTime(Date createTime) {
        if(null == createTime) {
           this.createTime = null;
        } else {
            this.createTime = (Date) createTime.clone();
        }
    }

double between = (end.getTime() - begin.getTime()) / 1000.0;