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Group and Sum By Id
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| private Map<Integer, Integer> getGroupsById() { | |
| List<IdValue> values = Lists.newArrayList( | |
| new IdValue(1, 2), | |
| new IdValue(1, 6), | |
| new IdValue(3, 1), | |
| new IdValue(3, 3), | |
| new IdValue(5, 3), | |
| new IdValue(5, 10) | |
| ); | |
| Map<Integer, Integer> collect = values.stream() | |
| .collect(Collectors.groupingBy(IdValue::getId, Collectors.toList())) | |
| .entrySet() | |
| .stream() | |
| .collect(Collectors.toMap( | |
| Map.Entry::getKey, | |
| entry -> entry.getValue() | |
| .stream() | |
| .mapToInt(IdValue::getValue) | |
| .sum() | |
| ) | |
| ); | |
| collect.forEach((key, value) -> log.info("group ==> {} {} ", key, value)); | |
| return collect; | |
| } | |
| private static class IdValue { | |
| private int id; | |
| private int value; | |
| public IdValue(int id, int value) { | |
| this.id = id; | |
| this.value = value; | |
| } | |
| public int getId() { | |
| return id; | |
| } | |
| public void setId(int id) { | |
| this.id = id; | |
| } | |
| public int getValue() { | |
| return value; | |
| } | |
| public void setValue(int value) { | |
| this.value = value; | |
| } | |
| } |
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