Java HashMap getOrDefault() Method

The HashMap.getOrDefault() method in Java is used to return the value to which the specified key is mapped, or the default value if the map contains no mapping for the key.

Table of Contents

1. Introduction
2. getOrDefault Method Syntax
3. Examples
   • Retrieving Values with a Default
   • Real-World Use Case: Handling Missing Employee Records
4. Conclusion

Introduction

The HashMap.getOrDefault() method is a member of the HashMap class in Java. It allows you to retrieve the value associated with a specific key, or return a default value if the key is not present in the map. This can be useful for handling cases where a key might not be present without throwing an exception or returning null.

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 map contains no mapping for the key.
• The method returns the value associated with the specified key, or the defaultValue if the map contains no mapping for the key.

Examples

Retrieving Values with a Default

The getOrDefault method can be used to retrieve the value associated with a specific key, or return a default value if the key is not present.

Example

import java.util.HashMap;
import java.util.Map;

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

        // Adding entries to the HashMap
        countries.put("India", "IN");
        countries.put("United States", "US");
        countries.put("Canada", "CA");

        // Retrieving values with a default value
        String indiaCode = countries.getOrDefault("India", "Unknown");
        String brazilCode = countries.getOrDefault("Brazil", "Unknown");

        // Printing the results
        System.out.println("Country code for India: " + indiaCode);
        System.out.println("Country code for Brazil: " + brazilCode);
    }
}

Output:

Country code for India: IN
Country code for Brazil: Unknown

Real-World Use Case: Handling Missing Employee Records

In a real-world scenario, you might use the getOrDefault method to handle cases where an employee ID might not be present in the employee database, returning a default message instead.

Example

import java.util.HashMap;
import java.util.Map;

public class EmployeeRecordRetrieval {
    public static void main(String[] args) {
        // Creating a Map with String keys (employee IDs) and String values (employee names)
        Map<String, String> employeeDatabase = new HashMap<>();

        // Adding entries to the HashMap
        employeeDatabase.put("E001", "Ravi Kumar");
        employeeDatabase.put("E002", "Priya Sharma");
        employeeDatabase.put("E003", "Vijay Singh");

        // Employee ID to be searched
        String employeeIdToSearch1 = "E002";
        String employeeIdToSearch2 = "E004";

        // Retrieving the employee name using the employee ID, with a default message
        String employeeName1 = employeeDatabase.getOrDefault(employeeIdToSearch1, "Employee not found");
        String employeeName2 = employeeDatabase.getOrDefault(employeeIdToSearch2, "Employee not found");

        // Printing the employee names
        System.out.println("Employee ID " + employeeIdToSearch1 + ": " + employeeName1);
        System.out.println("Employee ID " + employeeIdToSearch2 + ": " + employeeName2);
    }
}

Output:

Employee ID E002: Priya Sharma
Employee ID E004: Employee not found

Conclusion

The HashMap.getOrDefault() method in Java provides a way to retrieve the value associated with a specific key, or return a default value if the key is not present in the map. By understanding how to use this method, you can handle cases where a key might not be present without throwing an exception or returning null. This method is useful in various scenarios, such as handling missing records, providing default values, and managing collections of data.