subtitude keys and values in TreeMap with other TreeMap in Java

Question

Assuming I have a TreeMap<String,List<String> first; and TreeMap<String,String> Origin; And each key and each value in first has an equivalent key in origin. How can I substitute key and values of first with related value from Origin? For example

first {a = [b,c,d], e = [ f,g,h]}
origin {a=a1,b=b1,c=c1,d=d1,e = e1, g = g1, h=h1}

I need to get this TreeMap DesiredMap {[a1 =b1,c1,d1],[e1 = f1,g1,h1]}

Answer 1

You have to iterate over the entries on your first TreeMap.

for(Map.Entry<String, List<String>> entry : first.entrySet()) {

For each entry grab the oldKey and the oldValues.

String oldKey= entry.getKey();
List<String> oldValues= entry.getValue();

Create the newKey

String newKey = origin.get(oldKey);           

Then iterate over each value s in oldValues to get the newValue from the origin in order to create the List of newValues

List<String> newValues = new ArrayList<>();
for(String s : oldValues) {
    newValues.add(origin.get(s));
}

Now that you have the newKey and the newValues put them in your result TreeMap.

result.put(newKey, newValues);

Go to the next entry and repeat!