Sum values of arraylist in hashmap java

Question

I want to sum values of arraylist in hashmap java. Following is my code:

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));
}

Input keys and values are like this:

1 : 1, 2, 3
2 : 4, 5, 6
1 : 1, 2, 3

The results come out like this:

1 : [1, 2, 3, [[1, 2, 3]]]
2 : [4, 5, 6]

I want result to come out like this:

1 : [2, 4, 6]   //summary of values in arraylist of same key
2 : [4, 5, 6]

How should I sum each values in arraylist of same key in hashmap?

In your code, hm.containsKey(dArray[i]), you are adding the array to the list. I think this is where you need to SUM the values of the array elements. — Vishal
– Vishal, Commented Jul 6, 2016 at 5:32
@Yuki probably show us a trimmed down version of what these arrays contain? — Samuel Toh
– Samuel Toh, Commented Jul 6, 2016 at 6:19

RE60K · Accepted Answer · 2016-07-06 06:25:14Z

1

I think I would've done like this:

    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();

Input:

1 : 1, 2, 3
2 : 4, 5, 6
1 : 1, 2, 3

Output:

1 : [2, 4, 6]
2 : [4, 5, 6]

answered Jul 6, 2016 at 6:25

RE60K

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3 Comments

Yuki Over a year ago

I can't write <>, : symbol.

RE60K Over a year ago

@Yuki what? why not?

Yuki Over a year ago

I have no idea! I developed Java on websphere studio application developer and Java version is J2RE 1.4.1, Java platform is 5.1.

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