Java Program to Get key from HashMap using the value

JavaCampus InterviewServer Side ProgrammingProgramming

In this article, we will understand how to get key from HashMap using the value. Java HashMap is a hash table based implementation of Java's Map interface. It is a collection of key-value pairs.

Below is a demonstration of the same −

Suppose our input is

Input HashMap: {Java=8, Scala=5, Python=15}
Key: 8

The desired output would be

The value of Key: 8 is Java

Algorithm

Step 1 - START
Step 2 - Declare namely
Step 3 - Define the values.
Step 4 - Create a HashMap of integer and string values and initialize elements in it using the ‘put’ method.
Step 5 - Define a key value.
Step 6 - Iterate over the elements of HashMap, and check if the key previously defined is present in the HashMap.
Step 7 - If found, break away from the loop.
Step 8 - Display the result
Step 9 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

import java.util.HashMap;
import java.util.Map.Entry;
public class Demo {
   public static void main(String[] args) {
      System.out.println("The required packages have been imported");
      HashMap<String, Integer> input_map = new HashMap<>();
      input_map.put("Scala", 5);
      input_map.put("Java", 8);
      input_map.put("Python", 15);
      System.out.println("The HashMap is defined as: " + input_map);
      Integer Key = 8;
      for(Entry<String, Integer> entry: input_map.entrySet()) {
         if(entry.getValue() == Key) {
            System.out.println("\nThe value of Key: " + Key + " is " + entry.getKey());
            break;
         }
      }
   }
}

Output

The required packages have been imported
The HashMap is defined as: {Java=8, Scala=5, Python=15}

The value of Key: 8 is Java

Example 2

Here, we encapsulate the operations into functions exhibiting object oriented programming.

import java.util.HashMap;
import java.util.Map.Entry;
public class Demo {
   static void get_value(HashMap<String, Integer> input_map,Integer Key){
      for(Entry<String, Integer> entry: input_map.entrySet()) {
         if(entry.getValue() == Key) {
            System.out.println("\nThe value of Key: " + Key + " is " + entry.getKey());
            break;
         }
      }
   }
   public static void main(String[] args) {
      System.out.println("The required packages have been imported");
      HashMap<String, Integer> input_map = new HashMap<>();
      input_map.put("Scala", 5);
      input_map.put("Java", 8);
      input_map.put("Python", 15);
      System.out.println("The HashMap is defined as: " + input_map);
      Integer Key = 8;
      get_value(input_map, Key);
   }
}

Output

The required packages have been imported
The HashMap is defined as: {Java=8, Scala=5, Python=15}

The value of Key: 8 is Java
raja
Updated on 30-Mar-2022 10:40:31

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