Map entrySet() method in Java with Examples

The entrySet() method of the java.util.Map interface returns a set view of all key–value mappings in the map, where each element is a Map.Entry<K, V>.

• Each Map.Entry represents a single key–value pair from the map.
• It allows simultaneous access to both keys and values during iteration.
• More efficient than keySet() when values are also required, as it avoids extra get() calls.

1 : Java
2 : Python

Explanation:

• entrySet() returns a set view of all key–value pairs in the map.
• Each element in the set is a Map.Entry object containing a key and its corresponding value.
• This approach allows efficient iteration when both keys and values are required.

Syntax

map.entrySet()

• Parameters: The method does not take any parameter.
• Return Value: The method returns a set having same elements as the hash map. Below programs illustrate the java.util.Map.entrySet() Method:

Note: The returned set is backed by the map, meaning changes to the map are reflected in the set and vice versa.

Example: Iterating Over a Map Using entrySet()

1 = Java
2 = Python
3 = C++

Explanation:

• entrySet() returns a set of key–value pairs.
• Each iteration gives a Map.Entry object.
• getKey() retrieves the key, and getValue() retrieves the value.

Example: Modifying Values Using entrySet()

{Apple=15, Banana=10}

Explanation:

• setValue() updates the value of the current entry.
• Since entrySet() is backed by the map, changes reflect in the original map.

entrySet() vs keySet()