Java-8 Lambda Expression Tutorial - Iterate Over Map Using Lambda Expression

A map is an object that maps keys to values. A map cannot contain duplicate keys: Each key can map to at most one value.

In java we iterate over map using for each loop.But in java 8 we can iterate over map in another way using lambda Expression.

Below is Simple Example of How Iterate over map using classic method and lambda expression.

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package com.kodemaker; import java.util.HashMap; import java.util.Map; public class IterateOverMapUsingLambdaExpression { public static void main(String[] args) { Map<Integer,String> mapOfStudent = new HashMap<Integer,String>(){{ put(1 ,"A"); put(2 ,"B"); put(3 ,"C");}}; //Simple Iteration Method over map System.out.println("Simple Method -"); for(Integer key : mapOfStudent.keySet()){ System.out.println("key :"+key+" Value :"+mapOfStudent.get(key)); } //Iterate over map using lambda expression System.out.println("Using Lambda Expression -"); mapOfStudent.forEach((key, value) ->System.out.println("key :"+key+" Value :"+mapOfStudent.get(key))); } }

Output :-

Simple Method -
key :1 Value :A
key :2 Value :B
key :3 Value :C
Using Lambda Expression -
key :1 Value :A
key :2 Value :B
key :3 Value :C