java1.8從list集合中抽取某個字段轉為新的集合以及把list集合按某個字段進行分組
從list集合中抽取getId轉為新的集合: List<NatCustomers> natCustomersList = natCustomersService.queryListByPage(0,1000); List<Integer> customerIds ...
從list集合中抽取getId轉為新的集合: List<NatCustomers> natCustomersList = natCustomersService.queryListByPage(0,1000); List<Integer> customerIds ...
fieldName:替換成相應的字段 ...
了變化) 查詢出來的結果集中會多一個count字段,這個字段就是將分組后的數據按照我們的排序規 ...
分組前數據: [ {"f1":"q","f2":"w","f3":"e","f4":"r"}, {"f1":"q","f2":"w","f3":"e","f4":"r"}, {"f1":"w","f2":"w","f3":"e","f4":"r"}, {"f1":"w","f2":"w","f3 ...
變型: 遍歷:數組或對象 總結: 首先拿到的是一堆未分組的數組:[{...}]; 其次根據某個字段進行分組等到: 1.對象:{key:[...]} 2.新數組:[ { name:key,data ...
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<?php $arr = [ [ 'id'=>1, 'name'=>'Tom' ], ...
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