map Iterate in Java 20

Java 20 does not exist and the latest Java version as of November 2021 is Java 17. Nevertheless, I will provide examples on how to iterate over a hash (also known as a HashMap) in Java using both its key-value pairs and its values.

Iterating over the key-value pairs:

import java.util.HashMap;
import java.util.Map;
public class HashIteration {

    public static void main(String[] args) {

        Map data = new HashMap<>();

        data.put("John", 21);

        data.put("Jane", 19);

        data.put("Joe", 23);

        data.put("Jill", 20);
for (Map.Entry entry : data.entrySet()) {

            String name = entry.getKey();

            int age = entry.getValue();

            System.out.println(name + " is " + age + " years old");

        }

    }

}

Output:

John is 21 years old

Jane is 19 years old

Joe is 23 years old

Jill is 20 years old

In this example, the HashMap contains names and ages of 4 individuals. To iterate over the key-value pairs in the HashMap, we use a for loop and the entrySet() method of the HashMap to get a set of all the key-value pairs. Inside the loop, we get the key and value of each pair using the getKey() and getValue() methods of the Map.Entry class.

Iterating over the values:

import java.util.HashMap;
import java.util.Map;
public class HashIteration {

    public static void main(String[] args) {

        Map data = new HashMap<>();

        data.put("John", 21);

        data.put("Jane", 19);

        data.put("Joe", 23);

        data.put("Jill", 20);
for (int age : data.values()) {

            System.out.println(age);

        }

    }

}

Output:

21

19

23

20

To iterate over the values in the HashMap, we can use a for loop and the values() method of the HashMap to get a collection of all the values. Inside the loop, we can simply use each value.