java.util.Dictionary

By / 27 May 2025 / 2 minutes of reading

Dictionary is an abstract class in java.util (predecessor of Map interface).It represents a key-value pair data structure.It is obsolete and rarely used in favor of the Map interface (especially HashMap).Hashtable is a concrete subclass of Dictionary.

Commonly Used Constructors and Methods

Note: Dictionary uses Enumeration, not Iterator.

Simple Program — Dictionary via Hashtable

import java.util.Dictionary;
import java.util.Hashtable;
import java.util.Enumeration;

public class DictionaryExample {
    public static void main(String[] args) {
        Dictionary<String, String> countryCapital = new Hashtable<>();

        countryCapital.put("India", "New Delhi");
        countryCapital.put("USA", "Washington D.C.");
        countryCapital.put("Japan", "Tokyo");

        System.out.println("Country-Capital Pairs:");
        Enumeration<String> keys = countryCapital.keys();

        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            System.out.println(key + " -> " + countryCapital.get(key));
        }
    }
}

Output

Country-Capital Pairs:
Japan -> Tokyo
USA -> Washington D.C.
India -> New DelhiCode language: CSS (css)

Problem Statement:

Lokesh and Balaji are designing a user role management system for an internal bank tool. They want to map usernames to roles (e.g., admin, manager, teller) using java.util.Dictionary. The system must:

  • Store predefined users and their roles
  • Allow querying a user’s role
  • Print all usernames and roles
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.Enumeration;
import java.util.Scanner;

public class UserRoleManager {
    public static void main(String[] args) {
        Dictionary<String, String> userRoles = new Hashtable<>();

        // Predefined users
        userRoles.put("lotusjavaprince", "Admin");
        userRoles.put("mahesh", "Manager");
        userRoles.put("anita", "Teller");
        userRoles.put("rajesh", "Customer Support");

        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter username to check role: ");
        String username = scanner.nextLine().toLowerCase();

        if (userRoles.get(username) != null) {
            System.out.println("Role of " + username + " is: " + userRoles.get(username));
        } else {
            System.out.println("User not found!");
        }

        System.out.println("\nAll User-Role Pairs:");
        Enumeration<String> keys = userRoles.keys();
        while (keys.hasMoreElements()) {
            String user = keys.nextElement();
            String role = userRoles.get(user);
            System.out.println(user + " -> " + role);
        }

        scanner.close();
    }
}
Enter username to check role: Mahesh
Role of mahesh is: Manager

All User-Role Pairs:
rajesh -> Customer Support
anita -> Teller
mahesh -> Manager
lotusjavaprince -> Admin

The java.util.Dictionary class is a legacy abstract class designed for handling key-value pairs, similar in purpose to modern Map interfaces. While once widely used, it has now been largely replaced by more robust, efficient, and flexible alternatives like HashMap and LinkedHashMap.

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