How to get keys and values from Map in Java?

January 20, 2023

In this section, we will show you how to get keys and values from Map in Java.

Java 8 Example

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

public class Main {

    public static void main(String[] args) {

        Map<String, String> map = new HashMap<>();
        map.put("host", "knowledgefactory.net");
        map.put("username", "knowledgefactory");
        map.put("password", "mypassword");

        // Java 8
        map.forEach((k, v) -> {
            System.out.println("Key: " + k + ", Value: " + v);
        });

    }
}

Console Output:

Key: password, Value: mypassword
Key: host, Value: knowledgefactory.net
Key: username, Value: knowledgefactory

Old style

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class Main {

    public static void main(String[] args) {

        Map<String, String> map = new HashMap<>();
        map.put("host", "knowledgefactory.net");
        map.put("username", "knowledgefactory");
        map.put("password", "mypassword");

        // Get keys and values
        for (Map.Entry<String, String> entry : map.entrySet()) {
            String k = entry.getKey();
            String v = entry.getValue();
            System.out.println("Key: " + k + ", Value: " + v);
        }

        // Get all keys
        Set<String> keys = map.keySet();
        for (String k : keys) {
            System.out.println("Key: " + k);
        }

        // Get all values
        Collection<String> values = map.values();
        for (String v : values) {
            System.out.println("Value: " + v);
        }

    }
}

Console Output:

Key: password, Value: mypassword
Key: host, Value: knowledgefactory.net
Key: username, Value: knowledgefactory
Key: password
Key: host
Key: username
Value: mypassword
Value: knowledgefactory.net
Value: knowledgefactory

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