How to Retrieve Keys from a HashMap in Java?

How can I retrieve the keys from a HashMap in Java?

private Map<String, Integer> team1 = new HashMap<>();

team1.put("United", 5);
// How to get keys?

In Java, the HashMap class provides a method to retrieve a set of keys contained in the map. This is achieved using the `keySet()` method, which returns a Set view of the keys. Here's how you can do it step by step.

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        Map<String, Integer> team1 = new HashMap<>();
        team1.put("United", 5);
        team1.put("City", 3);
        team1.put("Chelsea", 4);

        // Retrieve keys
        Set<String> keys = team1.keySet();
        for (String key : keys) {
            System.out.println(key);
        }
    }
}

Causes

• The original code is trying to use a non-existent method 'getKey()' which does not exist in the HashMap API.
• Understanding the HashMap methods like keySet(), values(), and entrySet() is crucial for effective data retrieval.

Solutions

• Use the `keySet()` method to obtain a Set of keys from the HashMap.
• Iterate through the Set to access the individual keys.

Mistake: Using 'getKey()' method instead of 'keySet()' to retrieve keys.

Solution: Always use the `keySet()` method to retrieve keys from a HashMap.

Mistake: Assuming the order of keys is maintained in the HashMap.

Solution: Remember that HashMap does not guarantee any specific order of its keys.