Java HashMap getOrDefault() Method

The HashMap.getOrDefault(Object key, V defaultValue) method in Java is used to return the value to which the specified key is mapped, or defaultValue if the map contains no mapping for the key. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. getOrDefault Method Syntax
3. Examples
   • Retrieving Values with Default in a HashMap
   • Real-World Use Case: Default Product Price
4. Conclusion

Introduction

The getOrDefault() method is a member of the HashMap class in Java. It provides a way to retrieve the value associated with a specified key, returning a default value if the key is not found. This is useful for avoiding null values and providing a fallback when the key is not present in the map.

getOrDefault() Method Syntax

The syntax for the getOrDefault method is as follows:

public V getOrDefault(Object key, V defaultValue)

• The method takes two parameters:
  • key of type Object, which represents the key whose associated value is to be returned.
  • defaultValue of type V, which represents the value to be returned if the key is not found.
• The method returns the value associated with the specified key, or defaultValue if the map contains no mapping for the key.

Examples

Retrieving Values with Default in a HashMap

The getOrDefault method can be used to retrieve the value associated with a key, with a fallback to a default value if the key is not found.

Example

import java.util.HashMap;

public class GetOrDefaultExample {
    public static void main(String[] args) {
        // Creating a HashMap with String keys and Integer values
        HashMap<String, Integer> people = new HashMap<>();

        // Adding entries to the HashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Retrieving values with default
        int ageRavi = people.getOrDefault("Ravi", 0);
        int ageAmit = people.getOrDefault("Amit", 0); // Key "Amit" does not exist

        // Printing the results
        System.out.println("Age of Ravi: " + ageRavi);
        System.out.println("Age of Amit: " + ageAmit); // This will print the default value 0
    }
}

Output:

Age of Ravi: 25
Age of Amit: 0

Real-World Use Case: Default Product Price

In a real-world scenario, you might use the getOrDefault method to retrieve the price of a product, returning a default price if the product ID is not found in the database.

Example

import java.util.HashMap;

public class DefaultProductPrice {
    public static void main(String[] args) {
        // Creating a HashMap with String keys (product IDs) and Integer values (prices)
        HashMap<String, Integer> productPrices = new HashMap<>();

        // Adding entries to the HashMap
        productPrices.put("P001", 1000);
        productPrices.put("P002", 1500);
        productPrices.put("P003", 2000);

        // Default price to be used if the product ID is not found
        int defaultPrice = 500;

        // Retrieving product prices with default
        int priceP001 = productPrices.getOrDefault("P001", defaultPrice);
        int priceP004 = productPrices.getOrDefault("P004", defaultPrice); // Key "P004" does not exist

        // Printing the results
        System.out.println("Price of P001: " + priceP001);
        System.out.println("Price of P004: " + priceP004); // This will print the default price
    }
}

Output:

Price of P001: 1000
Price of P004: 500

Conclusion

The getOrDefault() method in Java provides a way to retrieve the value associated with a specified key, returning a default value if the key is not found. By understanding how to use this method, you can efficiently manage missing keys and provide fallback values, avoiding potential null values in your application. This method is useful in various scenarios, such as providing default settings, handling missing data, or setting default values for computations.