我想在arraylist
中对hashmap java
的值求和。以下是我的代码:
Map hm = new HashMap();
for(int i=0; i<dataArray().length; i++){
Arraylist valueHashMap = new Arraylist();
valueHashMap.add(0, aArray[i]);
valueHashMap.add(1, bArray[i]);
valueHashMap.add(2, cArray[i]);
if (hm.containsKey(dArray[i])){
Arraylist newOne = new Arraylist();
newOne.add(hm.get(dArray[i]));
valueHashMap.add(newOne);
hm.put(dArray[i], valueHashMap);
}else{
hm.put(dArray[i], valueHashMap);
}
}
Iterator iterator = hm.keySet().iterator();
while(iterator.hasNext()){
String key = iterator.next().toString();
System.out.println(key + " " + hm.get(key));
}
输入键和值如下:
1 : 1, 2, 3
2 : 4, 5, 6
1 : 1, 2, 3
结果如下:
1 : [1, 2, 3, [[1, 2, 3]]]
2 : [4, 5, 6]
我希望结果像这样出来:
1 : [2, 4, 6] //summary of values in arraylist of same key
2 : [4, 5, 6]
如何对arraylist
中相同键的hashmap
中的每个值求和?
答案 0 :(得分:1)
我想我会这样做:
Scanner sc = new Scanner(System.in);
Map<String, int[]> m = new HashMap<>();
int n = 3;
for (int i = 0; i < n; i++) {
String[] s = sc.nextLine().split("[,\\s:]+");
int[] arr = new int[s.length - 1];
boolean cn = m.containsKey(s[0]);
for (int j = 0; j < arr.length; j++) {
arr[j] = Integer.parseInt(s[j + 1]) + ((cn) ? m.get(s[0])[j] : 0);
}
m.put(s[0], arr);
}
for (String s : m.keySet()) {
System.out.println(s + " : " + Arrays.toString(m.get(s)));
}
sc.close();
输入:
1 : 1, 2, 3
2 : 4, 5, 6
1 : 1, 2, 3
输出:
1 : [2, 4, 6]
2 : [4, 5, 6]