Dictionaries (HashMap) in Java

In Java, a HashMap works like a dictionary — it stores key-value pairs where each key maps to a value. You need to import java.util.HashMap.

HashMap<String, Integer> scores = new HashMap<>();
scores.put("Alice", 95);
scores.put("Bob", 87);
scores.put("Charlie", 72);

The type parameters <String, Integer> specify the key type and value type. Use put(key, value) to add entries:

HashMap<String, Integer> ages = new HashMap<>();
ages.put("Alice", 25);
ages.put("Bob", 30);
System.out.println(ages.get("Alice"));  // 25
System.out.println(ages.size());        // 2