How To Iterate Map In Java Using Iterator

Introduction

Maps are a fundamental data structure in Java, used to store and organize data in key-value pairs. Iterating through a map can be a useful operation when you need to access or manipulate the values stored in the map. In this article, we will discuss how to iterate through a map in Java using the Iterator interface.

Using the Iterator Interface

The Iterator interface in Java provides a way to iterate through a collection of objects. To use the Iterator interface to iterate through a map, we first need to obtain a reference to the map’s iterator. We can do this using the iterator() method of the Map interface.

Example:

Map map = new HashMap<>();

Iterator> iterator = map.entrySet().iterator();

Using the Entry Set

The entrySet() method of the Map interface returns a set view of the key-value pairs contained in the map. We can use this set view to obtain an iterator that can be used to iterate through the map.

Example:

Map map = new HashMap<>();

Set> set = map.entrySet();

Iterator> iterator = set.iterator();

Using the For-Each Loop

Java also provides a convenient way to iterate through a map using the for-each loop. The for-each loop allows us to iterate through the map’s key-value pairs without the need for an explicit iterator.

Example:

Map map = new HashMap<>();

for(Map.Entry entry : map.entrySet()) {

 String key = entry.getKey();

 Integer value = entry.getValue();

 // Do something with key and value

}

Conclusion

Iterating through a map in Java is a common operation when working with key-value pairs. We have discussed three different ways to iterate through a map using the Iterator interface, the entry set, and the for-each loop. By using these techniques, you can easily access and manipulate the values stored in a map.