How to print a database in HashMap that is less than or equals to the given limit?

I am trying to make a database with HashMap that contains the name and weight of Dinos. I want to set a weight limit on printMatchingDinos() method, such that only Dinos with weight less than or equals to the limit will be printed.

public class DinoDatabase {
private HashMap<String, Integer> listOfDinos = new HashMap<>();
private String name;
private int weight;
public DinoDatabase() {
Map<String, Integer> listOfDinos = new HashMap<String, Integer>();
this.name = name; // Dino's name
this.weight = weight; // Dino's weight
}
// Add dino to the database
public void addDino(String name, int weight) {
if (!listOfDinos.containsKey(name)) {
listOfDinos.put(name, weight);
System.out.println(name + " added. Weight: " + weight + "kg");
}
else {
System.out.println(name + " cannot be added. It is already in the database!");
}
}
// Print Dino which has a weight less than or equals to the limit
public void printMatchingDinos(int limit) {
if (weight > limit) {
listOfDinos.remove(name, weight);
for (String name : listOfDinos.keySet()) {
System.out.println(listOfDinos.get(name));
}
}
else {
System.out.println("No Dino with given standard");
}
}
public static void main(String[] args) {
DinoDatabase db = new DinoDatabase();
db.addDino("Dravidosaurus", 907);
db.addDino("Eouplocephalus", 3175);
db.addDino("Tyrex", 1000);
db.printMatchingDinos(1000);
}
}
/* Output:
Dravidosaurus added. Weight: 907kg
Eouplocephalus added. Weight: 3175kg
Tyrex added. Weight: 1000kg
No Dino with given standard */

The expected output is

Dravidosaurus added. Weight: 907kg
Tyrex added. Weight: 1000kg

You seem rather confused on what this class is supposed to represent.

Your class has both a name and weight field, so, apparently, a DinoDatabase instance represents a single dinosaur. Yet, it also has a map that maps names to weights, so, it also represents the concept of a dino database.

That doesn't make sense.

You should probably have two classes here: public class Dino {String name; int weight; } and public class DinoDatabase { Map<String, Dino> dinos; }. Smushed together, that makes no sense and is confusing you a lot. For example, in your constructor, you write this.name = name; which does nothing whatsoever, it's assigning the name field to itself. It only makes sense if there is a parameter named name. You could get away with making no Dino class at all and sticking with a Map<String, Integer> for your dinos, but it does mean you're committed to only storing the weight of dinos and you can't conveniently add more properties, such as which era they were alive in, or whether they could fly or not.

Given that you're using a hashmap, there is no DB smarts you can apply here; the only way to find all dinos that match a certain condition, unless the condition is: "Whose name is exactly equal to this string", is to loop through the entire map and return all matching entries. Actual DBs are smarter, in that you can add an index so that such queries can be fast even if you have millions of dinos, but that involves programming concepts that are considerably more complicated than what's going on in this code. I'd assume the intent of this exercise is just to write it simply, and loop through every dino, returning only the ones that match the condition. This means you need to make an ArrayList object (or another collection of your choice), loop through, add only the matches ones, then return that collection.

Currently printMatchingDinos not filtering anything now. You don't need to remove anything to print out. You can iterate entrySet of listOfDinos and just put a condition to filter out in the loop when printing.

public void printMatchingDinos(int limit) {
for (Map.Entry<String, Integer> entry : listOfDinos.entrySet()) {
if (entry.getValue() <= limit)
System.out.println(entry.getKey() + "- Weight: " + entry.getValue() + "kg");
}
}

Though your requirement doesn't match the expected output. Those lines are printed when addDino called.

Suggestion: It's better to create a class for Dino with field name & weight and DinoDatabase may contain HashMap of Key-Dino pair as a field where Key is uniquely identify every Dino.