Java HashMap entrySet() Usage and Example

Java HashMap Methods

The Java HashMap entrySet() returns a collection view of all the mappings (entries) present in the hash map.

The syntax of the entrySet() method is:

hashmap.entrySet()

entrySet() parameter

The entrySet() method does not take any parameters.

entrySet() return value

• Returns a set view of all entries in the hashmap

Note: set view means that all entries in the hashmap are considered as a collection. Entries are not converted to a collection.

Example1: Java HashMap entrySet()

import java.util.HashMap;
class Main {
　　public static void main(String[] args) {
　　　　//　Create a HashMap
　　　　HashMap<String, Integer> prices = new HashMap<>();
　　　　//　Insert entries into HashMap
　　　　prices.put("Shoes",　200);
　　　　prices.put("Bag",　300);
　　　　prices.put("Pant",　150);
　　　　System.out.println("HashMap: ");　+　prices);
　　　　//Returns a set view of the map
　　　　System.out.println("Set view: ");　+　prices.entrySet());
　　}
}

Output Result

HashMap: {Pant=150, Bag=300, Shoes=200}
Set view: [Pant=150, Bag=300, Shoes=200]

In the above example, we created a hash map named prices. Note the expression

prices.entrySet()

Here, the entrySet() method returns a view of the set of all entries from the hash map.

the entrySet() method can be used withfor-each loopused together to iterate over each entry in the hash map.

Example2: for-entrySet() method in each loop

import java.util.HashMap;
import java.util.Map.Entry;
class Main {
　　　　public static void main(String[] args) {
　　　　　　　　//　Create a HashMap
　　　　　　　　HashMap<String, Integer> numbers = new HashMap<>();
　　　　　　　　numbers.put("One",　1);
　　　　　　　　numbers.put("Two",　2);
　　　　　　　　numbers.put("Three",　3);
　　　　　　　　System.out.println("HashMap: ");　+　numbers);
　　　　　　　　//Access each entry in the hashmap
　　　　　　　　System.out.print("Entries: ");
　　　　　　　　//entrySet() returns a view of the set of all entries
　　　　　　　　//for-each loop visits each entry in the view
　　　　　　　　for(Entry<String, Integer> entry: numbers.entrySet()) {
　　　　　　　　　　　　System.out.print(entry);
　　　　　　　　　　　　System.out.print(", ");
　　　　　　　　}
　　　　}
}

Output Result

HashMap: {One=1, Two=2, Three=3}
Entries: One=1, Two=2, Three=3,

In the above example, we imported the java.util.Map.Entry package. Map.Entry is a nested class of the Map interface. Note this line,

Entry<String, Integer> entry : numbers.entrySet()

Here, the entrySet() method returns a view of the collection of all entries. The Entry class allows us to store and print each entry in the view.

Related Reading

• HashMap keySet() - Return a view of the set of all keys

• HashMap values() - Return a view of the collection of all values

Java HashMap Methods