Java HashMap EntrySet

HashMap is a hash table based implementation of Map interface in Java. It uses a hash function to calculate the index of elements and stores them in a table. The EntrySet of a HashMap represents a set of key-value pairs stored in the HashMap. In this article, we will discuss the EntrySet in detail.

EntrySet

The EntrySet of a HashMap contains objects of the Map.Entry class. The Map.Entry interface is used to represent a key-value pair in a Map. The EntrySet provides a way to access the entries of a HashMap in a forward manner. The EntrySet interface contains methods to get a Set of keys, values or entries.

Here is an example of getting an EntrySet from a HashMap:

HashMap<Integer, String> map = new HashMap<Integer, String>();
map.put(1, "John");
map.put(2, "Peter");
map.put(3, "Sarah");
Set<Map.Entry<Integer, String>> entrySet = map.entrySet();

In the above example, we have created a HashMap and added some key-value pairs to it. Then we have called the entrySet() method to get the EntrySet of the HashMap. The entrySet() method returns a Set of the Map.Entry type.

Iterating over EntrySet

We can iterate over the EntrySet of a HashMap using a for-each loop. The EntrySet provides a way to access the key-value pairs of a HashMap. Here is an example:

HashMap<Integer, String> map = new HashMap<Integer, String>();
map.put(1, "John");
map.put(2, "Peter");
map.put(3, "Sarah");
Set<Map.Entry<Integer, String>> entrySet = map.entrySet();

for (Map.Entry<Integer, String> entry : entrySet) {
    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
}

In the above example, we have created a HashMap and added some key-value pairs to it. Then we have called the entrySet() method to get the EntrySet of the HashMap. We have iterated over the EntrySet using a for-each loop and printed the key-value pairs.

Conclusion

The EntrySet of a HashMap provides a way to access the key-value pairs stored in the HashMap. We can use the entrySet() method to get the EntrySet. The EntrySet contains objects of the Map.Entry class. We can iterate over the EntrySet using a for-each loop to access the key-value pairs.