Iterate through an attached hash file

Question

How can I iterate through a nested HashMap?

HashMap installed as follows:

 HashMap<String, HashMap<String, Student>> 

Where Student is an object containing the name variable. If, for example, my HashMap looked like this (the following code is not mine, it's just to simulate the contents of the contents of the hash map)

  hm => HashMap<'S', Hashmap<'Sam', SamStudent>> HashMap<'S', Hashmap<'Seb', SebStudent>> HashMap<'T', Hashmap<'Thomas', ThomasStudent>> 

How can I repeat all keys with a single letter, then each full key, and then pull out the student’s name?

Answer 1

 for (Map.Entry<String, HashMap<String, Student>> letterEntry : students.entrySet()) { String letter = letterEntry.getKey(); // ... for (Map.Entry<String, Student> nameEntry : letterEntry.getValue().entrySet()) { String name = nameEntry.getKey(); Student student = nameEntry.getValue(); // ... } } 

Answer 2

Java 8 lambdas and Map.forEach make bkail answer more concise:

 outerMap.forEach((letter, nestedMap) -> { //... nestedMap.forEach((name, student) -> { //... }); //... });