1. Java多个Map合并
// 多个Map<Long,Integer>, 根据key相同的,value累积求和;
public static Map mapCombine(List<Map<Long,Integer>> list) {
Map<Long, Integer> map = new HashMap<>();
for (Map<Long,Integer> m : list) {
Iterator<Long> it = m.keySet().iterator();
while (it.hasNext()) {
Long key = it.next();
if (!map.containsKey(key)) {
map.put(key, m.get(key));
} else {
map.put(key,(map.get(key)+m.get(key)));
}
}
}
return map;
}
2. Java中 map.values(Integer) 求和:
Integer totalCount = map.values().stream().mapToInt(Integer::intValue).sum(); //values求和
3. Map遍历:
map.entrySet().stream().forEach(x -> {
System.out.println("key: "+x.getKey()+", value: "+x.getValue());
});
4. Map 过滤:
result = map.entrySet().stream()
.filter(map -> "hello world".equals(map.getValue()))
.map(map -> map.getValue())
.collect(Collectors.joining()
);
参考:
https://blog.csdn.net/qq_24877569/article/details/52187388