Question

I would like to know how can I iterate in a 2Dimensional HashMap? I am creating an Object TrueStringMap2D that does the following: It will be a map 2D, i mean 2 keys and one value.

But the iterator implemented here is not functional.. i didnt know how to redefine the Iterator method in TrueStringMap2D :S (if possible should be remove in the iterator() functional)
Anyone can help?
Thankyou very much!!

Answer 1

I’ll reinterpret the question into something similar that I enjoy answering, and then hopefully the answer to that question is useful to you.

Here’s the question I’ll answer:

How do I write an iterator that iterates over all values in a Map<String, Map<String, String>>?

This is how I would solve it:

class TwoDimIterator implements Iterator<String> {

    Iterator<Map<String, String>> outerIter;
    Iterator<String> innerIter = Collections.<String>emptyList().iterator();

    public TwoDimIterator(Map<String, Map<String, String>> twoDimMap) {
        outerIter = twoDimMap.values().iterator();
        advanceInner();
    }

    @Override
    public boolean hasNext() {
        return innerIter.hasNext();
    }

    @Override
    public String next() {
         String toReturn = innerIter.next();
         advanceInner();
         return toReturn;
    }

    private void advanceInner() {
        while (!innerIter.hasNext()) {
            if (!outerIter.hasNext()) {
                innerIter = Collections.<String>emptyList().iterator();
                return;
            }
            innerIter = outerIter.next().values().iterator();
        }
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}

Test code:

class Test {

    public static void main(String[] args) {

        // Create a map
        Map<String, Map<String, String>> twoDimMap =
                new HashMap<String, Map<String, String>>();

        // Fill it
        Map<String, String> innerA = new HashMap<String, String>();
        innerA.put("1", "A1");
        innerA.put("2", "A2");

        Map<String, String> innerB = new HashMap<String, String>();
        innerB.put("1", "B1");
        innerB.put("2", "B2");

        twoDimMap.put("A", innerA);
        twoDimMap.put("B", innerB);

        // Create an iterator for the values:
        Iterator<String> twoDimIter = new TwoDimIterator(twoDimMap);
        while (twoDimIter.hasNext())
            System.out.println(twoDimIter.next());

    }
}

Output:

A2
A1
B2
B1