对象A具有time和value两个属性A a = {
"2008-1-01 01:1:21","4",
"2008-1-01 02:2:21","12",
"2008-1-01 03:3:21","42",
"2008-1-02 01:4:21","463",
"2008-1-02 01:11:21","4",
"2008-1-02 02:12:21","4",
"2008-1-03 03:13:21","4",
}//后面还有很多值
如何计算出这个月每天的平均值,然后生成一个新的ArrayList
"2008-1-01 01:1:21","4",
"2008-1-01 02:2:21","12",
"2008-1-01 03:3:21","42",
"2008-1-02 01:4:21","463",
"2008-1-02 01:11:21","4",
"2008-1-02 02:12:21","4",
"2008-1-03 03:13:21","4",
}//后面还有很多值
如何计算出这个月每天的平均值,然后生成一个新的ArrayList
把"2008-1-01 01:1:21","4",
分段取出(取出你要算平均数的数据) 来分别计算(这里要数据类型转换)计算完再转换回去
这里要用到正则(偶不熟悉O_O 据说这里的火龙果正则很厉害\(^o^)/)
直接用split取出"2008-1-01"的字符串作为key放入Hashmap就足够了.