Java 8 – How to find an entry based on the Value in a Map or HashMap ?

February 12, 2023 SJ Collection, Java 8 0

In this article, we will discuss how to find an entry based on the Value in a HashMap using Java 8 Stream

Find an entry based on Value in a HashMap :

To find an entry based on the Value,

  • First iterate through entrySet
  • Then get the entry by comparing the Value

Here, we will discuss 2 approaches to find an entry based on the Value from HashMap

  • Using Java 8 Stream
  • Before Java 8

1. Using Java 8 Stream :

  • Iterate through entry set using Stream and filter required entry by comparing Value using Stream.filter() method
  • Now there are 2 possibilities on comparison,
    • If the entry is present with the supplied Value, then corresponding entry will be printed to the console
    • If it is not present, nothing will be printed in the console
  • Note: If there are duplicate values for the different unique Keys, then it will print all entries corresponding to that Value

FindEntryBasedOnValueInMapUsingJava8Stream.java

package in.bench.resources.find.entry.map;

import java.util.HashMap;
import java.util.Map;

public class FindEntryBasedOnValueInMapUsingJava8Stream {

	public static void main(String[] args) {

		// 1. creating HashMap object of type <Integer, String>
		Map<Integer, String> populationCountry = new HashMap<>(); 


		// 1.1 adding key-value pairs to HashMap object
		populationCountry.put(220892331, "Pakistan");
		populationCountry.put(146748590, "Russia");
		populationCountry.put(213728559, "Brazil");
		populationCountry.put(382357386, "Indian");
		populationCountry.put(332429717, "America");


		// 1.2 print original Map entries
		System.out.println("1. Original Map Entries :- \n");


		// 1.3 print Map entries to console
		populationCountry.forEach((key, value) -> System.out.println(
				"Key : " + key  + "\t\t"  + "Value : "  + value
				));



		// 2. find Entry on the basis of Value
		String valueToFind = "Pakistan";


		// 2.1 print to console
		System.out.println("\n\n2. Entry which has Value '" + valueToFind + "'\n");


		// 2.2 Iterate and find Entry based on Value
		populationCountry
		.entrySet()
		.stream()
		.filter(entry -> entry.getValue().equals(valueToFind))
		.forEach(System.out::println);
	}
}

Output :

1. Original Map Entries :- 

Key : 382357386		Value : Indian
Key : 220892331		Value : Pakistan
Key : 146748590		Value : Russia
Key : 213728559		Value : Brazil
Key : 332429717		Value : America


2. Entry which has Value 'Pakistan'

220892331=Pakistan

2. Before Java 8 :

  • Iterate through entry set using enhanced for-loop and filter required entry by comparing Value using if–condition
  • Now there are 2 possibilities on comparison,
    • If the entry is present with the supplied Value, then corresponding entry will be printed to the console
    • If it is not present, nothing will be printed in the console
  • Note: If there are duplicate values for the different unique Keys, then it will print all entries corresponding to that Value

FindEntryBasedOnValueInMap.java

package in.bench.resources.find.entry.map;

import java.util.HashMap;
import java.util.Map;

public class FindEntryBasedOnValueInMap {

	public static void main(String[] args) {

		// 1. creating HashMap object of type <Integer, String>
		Map<Integer, String> populationCountry = new HashMap<>(); 


		// 1.1 adding key-value pairs to HashMap object
		populationCountry.put(220892331, "Pakistan");
		populationCountry.put(146748590, "Russia");
		populationCountry.put(213728559, "Brazil");
		populationCountry.put(382357386, "Indian");
		populationCountry.put(332429717, "America");


		// 1.2 print original Map entries
		System.out.println("1. Original Map Entries :- \n");


		// 1.3 print Map entries to console
		populationCountry.forEach((key, value) -> System.out.println(
				"Key : " + key  + "\t\t"  + "Value : "  + value
				));



		// 2. find Entry on the basis of Value
		String valueToFind = "Pakistan";


		// 2.1 print to console
		System.out.println("\n\n2. Entry which has Value '" + valueToFind + "'\n");


		// 2.2 Iterate and find Entry based on Value
		for(Map.Entry<Integer, String> entry : populationCountry.entrySet()) {

			if(entry.getValue().equals(valueToFind)) {
				System.out.println(entry);
			}
		}
	}
}

Output :

1. Original Map Entries :- 

Key : 382357386		Value : Indian
Key : 220892331		Value : Pakistan
Key : 146748590		Value : Russia
Key : 213728559		Value : Brazil
Key : 332429717		Value : America


2. Entry which has Value 'Pakistan'

220892331=Pakistan

Related Articles :

References :

Happy Coding !!
Happy Learning !!

Java 8 - How to remove an entry based on the Value in a Map or HashMap ?
Java 8 - How to remove an entry based on the Key in a Map or HashMap ?

Related posts:

  1. Java 8 – How to remove an entry based on the Value in a Map or HashMap ?
  2. Java 8 – How to find an entry based on the Key in a Map or HashMap ?
  3. Java 8 – How to remove an entry based on the Key in a Map or HashMap ?
  4. Java 8 – Find First and Last entries in a Map or HashMap ?