Java HashMap forEach() Usage and Example

Java HashMap Methods

Java HashMap forEach() method is used to perform a specified operation on each mapping of the hash map.

The syntax of forEach() method is:

hashmap.forEach(BiConsumer<K, V> action)

forEach() Parameters

• action - Operation performed on each mapping of HashMap

forEach() Return Value

The forEach() method does not return any value.

Example: Java HashMap forEach()

import java.util.HashMap;
class Main {
　　public static void main(String[] args) {
　　　　//　Creating HashMap
　　　　HashMap<String, Integer> prices = new HashMap<>();
　　　　//Inserting entries into HashMap
　　　　prices.put("Shoes",　200);
　　　　prices.put("Bag",　300);
　　　　prices.put("Pant",　150);
　　　　System.out.println("Market Price: ");　+　prices);
　　　　System.out.print("Discount Price: ");
　　　　//　Pass the lambda expression to forEach()
　　　　prices.forEach((key,　value)　->　{
　　　　　　//　Value Decrease10%
　　　　　　value　=　value　-　value　*　10/100;
　　　　　　System.out.print(key　+　"="　+　value　+　"　");
　　　　});
　　}
}

Output Result

Market Price: {Pant=150,　Bag=300,　Shoes=200}
Discount price:　Pant=135　Bag=270　Shoes=180

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

prices.forEach((key,　value)　->　{
　　value　=　value　-　value　*　10/100;
　　System.out.print(key　+　"="　+　value　+　"　");　　
});

We have setLambda expressionpassed as a parameter to the forEach() method. Here,

• The forEach() method executes the operation specified by the lambda expression for each entry of the hash table
  

• Lambda expressions will reduce each value10％, and print all keys and reduced values

For more information about lambda expressions, please visitJava Lambda Expressions.

Note: forEach() method with for-each loop is different. We can useJava for-each loopTraverse each entry of the hash table.

Java HashMap Methods