Facebook Twitter Instagram
    TecAdmin
    • Home
    • FeedBack
    • Submit Article
    • About Us
    Facebook Twitter Instagram
    TecAdmin
    You are at:Home»Programming»JAVA»Java HashMap – How to Get Key from Value

    Java HashMap – How to Get Key from Value

    By RahulApril 6, 20222 Mins Read

    Write a Java program to get keys from the hashmap using the value.

    Advertisement

    The HashMap class is available under the java.util package. It is pretty similar to HashTable, but the HashMap is unsynchronized and also allows to stole one null key.

    In this tutorial, you will learn Java examples to get keys from a HashMap based on a defined value.

    Get Key for a Value in HashMap

    The Entry interface provides a number of methods to access key values from a HashMap. The Entry.getValue() method returns the value based on the provided key.

    Here is an example Java program to initialize a HashMap and then iterate through all key-pair using for loop.

    Let’s create a file HashMapExample1.java in your system and add the below content.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    import java.util.HashMap;
    import java.util.Map.Entry;
     
    class HashMapExample1 {
      public static void main(String[] args) {
     
        // Define a hashmap
        HashMap<Integer, String> cities = new HashMap<>();
     
        // Adding key pair to hashmap  
        cities.put(101, "Delhi");
        cities.put(102, "New York");
        cities.put(103, "Peris");
        cities.put(104, "Denmark");
     
        // Define value to search key for
        String value = "Peris";
     
        // Iterate through hashmap using for loop
        for(Entry<Integer, String> entry: cities.entrySet()) {
          if(entry.getValue() == value) {
            System.out.println("The Key for '" + value + "' is " + entry.getKey());
            break;
          }
        }
      }
    }

    Save the file and close it.

    Now, compile the Java program and run. You will see the results below.

    Output:
    The Key for 'Peris' is 103

    Get All Key Values in HashMap

    Here is another example showing to get all key values from a Java HashMap.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    import java.util.HashMap;
     
    class HashmapExample2 {
      public static void main(String[] args) {
     
        // Define a hashmap
        HashMap<Integer, String> cities = new HashMap<>();
     
        // Adding key pair to hashmap  
        cities.put(101, "Delhi");
        cities.put(102, "New York");
        cities.put(103, "Peris");
        cities.put(104, "Denmark");
     
        // Print all hashmap key pairs
        System.out.println("HashMap: " + cities);
      }
    }

    Now, compile and run above Java program. You should see the results as below:

    Output:
    HashMap: {101=Delhi, 102=New York, 103=Peris, 104=Denmark}

    Wrap Up

    In this faq, you have learned an example to get the HashMap key based on a value in the Java programming language.

    HashMap Java
    Share. Facebook Twitter Pinterest LinkedIn Tumblr Email WhatsApp

    Related Posts

    Mastering Environment Variables in Java: A Comprehensive Guide

    Encapsulation in JAVA (With Example)

    Top Code Formatting Tips for Java Developers

    Add A Comment

    Leave A Reply Cancel Reply

    Advertisement
    Recent Posts
    • Setting and Getting the Default Timezone in Python
    • What is Media Access Control (MAC) Address?
    • What is Cross-Site Scripting (XSS)?
    • What is Content Security Policy (CSP)?
    • A User’s Guide to Understanding Redirection Operators in Bash
    Facebook Twitter Instagram Pinterest
    © 2023 Tecadmin.net. All Rights Reserved | Terms  | Privacy Policy

    Type above and press Enter to search. Press Esc to cancel.