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Java Program to Get key from HashMap using the value
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: 8The 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 JavaExample 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
Updated on: 30-Mar-2022
3K+ Views
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