Java LinkedHashMap迭代

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

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?

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();
    }
}