Java program to get the key from HashMap using value

Comprehensive Java Examples

In this example, we will learn how to get the key from a HashMap using values in Java.

To understand this example, you should know the followingJava ProgrammingTopic:

• Java HashMap

Example: Get the key from a HashMap with a given value

import java.util.HashMap;
import java.util.Map.Entry;
class Main {
　　public static void main(String[] args) {
　　　　//Create a hash map
　　　　HashMap<String, Integer> numbers = new HashMap<>();
　　　　numbers.put("One",　1);
　　　　numbers.put("Two",　2);
　　　　numbers.put("Three",　3);
　　　　System.out.println("HashMap: "　+　numbers);
　　　　//the value to search for its key
　　　　Integer value =　3;
　　　　//Iterate over each entry in the hashmap
　　　　for(Entry<String, Integer> entry: numbers.entrySet()) {
　　　　　　//If the given value is equal to the value from the entry
　　　　　　//Print the corresponding key
　　　　　　if(entry.getValue() == value) {
　　　　　　　　System.out.println(value　+　"The key of the value is:"　+　entry.getKey());
　　　　　　　　break;
　　　　　　}
　　　　}
　　}
}

Output Result

HashMap: {One=1, Two=2, Three=3}
3　The key of the value is: Three

In the above example, we created a hash map named numbers. Here, we want to get the value 3 The key. Note this line,

Entry<String, Integer> entry : numbers.entrySet()

Here, the entrySet() method returns a view of the set of all entries.

• entry.getValue() - Get the value from the entry

• entry.getKey() - Get the key from the entry

Inside the if statement, we check if the value in the entry is the same as the given value. If the value matches, we will get the corresponding key.

Comprehensive Java Examples