请教大家 java8 stream 的问题

[mawerss1]

下面的代码怎么用 stream 实现呢？想了半天绕不明白，stram api 用的太少了

public void countBlame(List<Blame> blames) {
    final HashMap<String, TotalResult> map = map();
    for (Blame author : blames) {
        if (map.containsKey(author.getName())) {
            final TotalResult totalResult = map.get(author.getName());
            totalResult.setRows(totalResult.getRows() + author.getRows());
        }else{
            final TotalResult totalResult = new TotalResult(author.getName(), 0, 0, author.getRows(), null);
            map.put(author.getName(), totalResult);
            results.add(totalResult);
        }
    }
}

private HashMap<String,TotalResult> map() {
    final HashMap<String, TotalResult> stringTotalResultHashMap = new HashMap<>();
    for (TotalResult result : results) {
        stringTotalResultHashMap.put(result.getName(), result);
    }
    return stringTotalResultHashMap;
}

[yemoluo]

第二个

results.stream().collect(Collectors.toMap(TotalResult::getName, result -> result))

[EXE]

results.stream().collect(Collectors.toMap(TotalResult::getName));

[Volio]

List<TotalResult> result = blames.stream().collect(Collectors.groupingBy(Blame::getName, Collectors.mapping(Blame::getRows, Collectors.reducing(0, Integer::sum)))).entrySet().stream().map(o -> new TotalResult(o.getKey(),0,0,o.getValue(),null)).collect(Collectors.toList());

[yidinghe]

优化后的代码是这样子的：
https://gitee.com/yidinghe/codes/6zekf0vcj495g32bln1p717



[yemoluo]

第一个

blames.stream().map(author => new TotalResult(author.getName(), 0, 0, author.getRows(), null)).collect(Collectors.toMap(TotalResult::getName, result -> result,(oldValue,newValue)-> {oldValue.setRows(oldValue.getRows() + newValue.getRows();return oldValue;}))

[mawerss1]

@yidinghe 醍醐灌顶，感谢老哥

[daemonk]

Map<String, TotalResult> map = blames.stream().collect(
Collectors.toMap(
Blame::getName,
blame -> new TotalResult(blame.getName(), 0, 0, blame.getRows(), null),
(tr1, tr2) -> {
tr1.setRows(tr1.getRows() + tr2.getRows());
return tr1;
}, HashMap::new));
List<TotalResult> results = new ArrayList<>(map.values());

[thinkmore]

为啥我看着 lambda 这么费力