java linkedhashmap iteration

Question

I have two hashmap

LinkedHashMap<String, int[]> val1 = new LinkedHashMap<String, int[]>();
LinkedHashMap<String, int> val2 = new LinkedHashMap<String, int>();

each hashmap has different key and values. I am trying to iterate over both hashmap at the same time and multiply each value of val1->int[] to val2->int

What is the easiest and fasted way to do it? I have thousands values in both hashmap.

Thanks

• Vance Maverick: Hmm, if they have different keys, then what does it mean to iterate over them at the same time? Say val1 has keys "a" and "b", while val2 has keys "X" and "Y". Does that mean you want to handle all four combinations (aX, aY, bX, bY), or what?
• Andrew White: Example versions of val1 and val2 with expected output will go a long way.
• Dhaivat Pandya: A LinkedHashMap has a iteration ordering, so, if he iterates from front to end, there's only one way he/she can do it.
• Tweet: logically val1 and val2 have relationship. val1->int[] contains multiple months' expense and val2->int contains the number of people. Now I want to iterate to multiple each month expense with number of people to get some values for further processing. val1 and val2 will always have same size

Answer 1

You are probably doing it wrong...

First, a HashMap can't store ints, it needs proper objects - like Integer – An array is an object, although it's hidden behind some syntactic sugar.

Here's how to loop over both maps, if they happens to have the same size, which is what I think you mean.

 Iterator<int[]> expenses = val1.values().iterator();
 Iterator<Integer> people = val2.values().iterator();
 assert val1.size() == val2.size() : " size mismatch";
 while (expenses.hasNext()) {
 int[] expensesPerMonth = expenses.next();
 int persons = people.next();
 // do strange calculation
 int strangeSum = 0;
 for (int idx = 0; idx < expensesPerMonth.length; idx++) {
 strangeSum += persons * expensesPerMonth[idx];
 }
 System.out.println("strange sum :" + strangeSum);
 }

But You should probably go back and rethink how you store your data – why are you using maps, and whats the key?

Wouldn't it be better to create an object that represents the combination of monthly expenses and number of people, for instance?

• Tweet: Thanks, I know it is wrong logic but I am not main developer. I am just maintaining.

Answer 2

AFAIK, a LinkedHashMap has iteration ordering. So, something like this may work:

Iterator myIt1 = val1.entrySet().iterator();
Iterator myIt2 = val2.entrySet().iterator();
while(val1.hasNext() && val2.hasNext()) {
 int myarray[] = val1.next();
 for(int i = 0; i<myarray.length; i++) {
 myarray[i] = myarray[i] * val2.next();
 }
}

• Tweet: for using val2.next(), it gives an error that The method next() is undefined for the type LinkedHashMap<String,int[]>
• I82Much: You're advancing iterator2 too often. (At least according to my interpretation of the question)
• Tweet: Could you please check your code again? it has several errors :(