Count

CountAggregate 实现了“全部计数”聚合。

类定义

    public static class CountAggregate implements Aggregate
    {
        public void initialize(Object val) 
        {
            count = 1;
        }
 
        public void accumulate(Object val) 
        {
            count += 1;
        }
         
        public Object result() 
        {
            return new Long(count);
        }
 
        public void merge(Aggregate other) 
        {
            count += ((CountAggregate)other).count;
        }
         
        long count;
    }