groovy groupby 多个字段

Question

我有一个列表，如:

def given  = [
            [Country:'Japan',Flag:'Yes',Event:'New Year', Amount:70],
            [Country:'china',Flag:'No',Event:'Spring Festival', Amount:60],
            [Country:'us',Flag:'Yes',Event:'Labour Day', Amount:10],
            [Country:'us',Flag:'Yes',Event:'Labour Day', Amount:20]
    ]

我期望的是:

[
        [Country:'Japan',Flag:'Yes',Event:'New Year', Amount:70],
        [Country:'china',Flag:'No',Event:'Spring Festival', Amount:60],
        [Country:'us',Flag:'Yes',Event:'Labour Day', Amount:30]
]

Answer 1

另一种可能性(但结果完全相同)

given.groupBy { it.subMap('Country', 'Flag', 'Event') }
     .collect { k, v -> k + [Amount: v.Amount.sum()] }