How would I go about iterating through a nested HashMap?
The HashMap
is setup like this:
HashMap<String, HashMap<String, Student>>
Where Student
is an object containing a variable name
. If for instance my HashMap looked like this (the following is not my code, it's just to simulate what the contents of the hashmap could be)
hm => HashMap<'S', Hashmap<'Sam', SamStudent>>
HashMap<'S', Hashmap<'Seb', SebStudent>>
HashMap<'T', Hashmap<'Thomas', ThomasStudent>>
How could I iterate through all of the single letter keys, then each full name key, then pull out the name of the student?
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();
// ...
}
}
...and the var
keyword in Java 10 can remove the generics verbosity:
for (var letterEntry : students.entrySet()) {
String letter = letterEntry.getKey();
// ...
for (var nameEntry : letterEntry.getValue().entrySet()) {
String name = nameEntry.getKey();
Student student = nameEntry.getValue();
// ...
}
}
Java 8 lambdas and Map.forEach
make bkail's answer more concise:
outerMap.forEach((letter, nestedMap) -> {
//...
nestedMap.forEach((name, student) -> {
//...
});
//...
});
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