java 中对于List集合,多字段分组,统计
1.java 中对于List集合,多字段分组,统计List<Student> list =new ArrayList<>();list.add(new Student("aaaa","aaaa","aaaa",15));list.add(new Student("aaaa","aaaa","aaaa",10));list.add(new Student("bbbb","bb
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1.java 中对于List集合,多字段分组,统计
List<Student> list =new ArrayList<>();
list.add(new Student("aaaa","aaaa","aaaa",15));
list.add(new Student("aaaa","aaaa","aaaa",10));
list.add(new Student("bbbb","bbbb","bbbb",5));
list.add(new Student("bbbb","bbbb","dddd",1));
Function<Student, List<Object>> keyExtractor = wr ->
Arrays.<Object>asList(wr.getName(), wr.getAge(), wr.getSex());
Map<List<Object>, Integer> aggregatedData = list.stream().collect(
Collectors.groupingBy(keyExtractor, Collectors.summingInt(Student::getSum)));
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