在Hashmap的Hashmap中查找最大值

Question

So I'm still relatively new to Java and this question may be fairly trivial but I'm having issues getting an answer.

I'm trying to find the max value within a hashmap I created. I initialized the hashmap and filled it but here's the structure:

HashMap<Double,HashMap<Double,Double>>

any help would be awesome.

Thanks!

EDIT: For clarification I would like to know the value of largest entry in the hashtable

Answer 1

So you have a root map full of nested maps. You will iterate on all values in the root map - fetching nested maps. And then iterate on each value on each nested map.

Compexity will be O(n) where n - number of all keys in the all nested maps plus number of keys in root map.

I think you can not find the max value faster if you use the HashMaps.

The code will look like:

final HashMap<Double, HashMap<Double, Double>> data = new HashMap<Double, HashMap<Double, Double>>();

Double prev = null;
for (final HashMap<Double, Double> nestedMap : data.values()) {
    for (final Double value : nestedMap.values()) {
        if (prev == null) {
            prev = value;
            continue;
        }
        prev = Math.max(value, prev);
    }
}

System.out.println("The max value is " + prev);