Introduction
If you are working with Java, you must have come across the Map interface. Map interface is one of the most commonly used interfaces in Java. It is used to store key-value pairs. To iterate through the values of a Map, we use an Iterator. In this article, we will be discussing how to use an Iterator with Map in Java.
Understanding Map in Java
Map is an interface in Java that is implemented by several classes such as HashMap, TreeMap, and LinkedHashMap. It stores the values in a key-value pair. The key is used to retrieve the value from the Map. The key must be unique in the Map.
Using Iterator with Map
To iterate through the values of a Map, we use an Iterator. An Iterator is an interface in Java that is used to iterate through the collection of objects. To use an Iterator with Map, we first need to get the Set of keys from the Map. We can get the Set of keys using the keySet() method of the Map interface.
Example
Let’s take an example to understand how to use an Iterator with Map in Java.
import java.util.HashMap; import java.util.Iterator; import java.util.Map; import java.util.Set; public class MapIteratorExample { public static void main(String[] args) { Map map = new HashMap<>(); map.put("A", 1); map.put("B", 2); map.put("C", 3); map.put("D", 4); map.put("E", 5); Set keySet = map.keySet(); Iterator iterator = keySet.iterator(); while (iterator.hasNext()) { String key = iterator.next(); Integer value = map.get(key); System.out.println(key + " : " + value); } } }
In the above example, we have created a Map object and added some key-value pairs to it. We have then used the keySet() method to get the Set of keys from the Map. We have then used an Iterator to iterate through the Set of keys. We have used the hasNext() method of the Iterator interface to check if there is any element left in the collection. We have used the next() method of the Iterator interface to get the next element in the collection. We have then used the get() method of the Map interface to get the value for the key.
Conclusion
In this article, we have discussed how to use an Iterator with Map in Java. We have seen how to get the Set of keys from the Map and how to iterate through the Set using an Iterator. We hope this article has helped you in understanding how to use an Iterator with Map in Java.