HashMap vs Hashtable: Unlocking the Best Choice for Efficient Data Management

HashMap vs Hashtable

• In Java, both HashMap and Hashtable are utilized to store key-value pairs in a collection, and both implement the Map interface.
• In spite of their likenesses, there are key contrasts that can impact which one to select for a particular situation.
• Understanding these contrasts is vital for making the correct choice based on execution necessities, thread safety, and information management needs.

Key Points of Difference:

1.Synchronization:

• HashMap isn’t synchronized by default, making it unacceptable for multi-threaded situations unless expressly synchronized externally.
• Hashtable is synchronized, meaning as it were one thread can access a method at a time, which makes it thread-safe but at the cost of execution.

2.Null Keys/Values:

• HashMap permits null keys and null values, making it more flexible once you got to store these values.
• Hashtable does not permit null keys or null values. Attempting to insert null into a Hashtable comes about in a NullPointerException.

3.Performance:

• HashMap is regularly speedier than Hashtable in most cases since it doesn’t have the overhead of synchronization.
• Hashtable is slower due to its synchronization mechanism, which makes a bottleneck when numerous threads attempt to get to the table concurrently.

4.Iterator vs. Enumeration:

• HashMap uses an Iterator that’s fail-fast. In case the map is altered whereas iterating, it throws a ConcurrentModificationException.
• Hashtable uses an Enumeration to repeat through its components, which isn’t fail-fast and does not throw exceptions for concurrent adjustments.

5.Thread Safety:

• HashMap isn’t thread-safe by default, and developers have to manage synchronization in case utilizing it in a multi-threaded environment.
• Then again, ConcurrentHashMap can be utilized for thread security in modern Java.
• Hashtable is thread-safe, but its utilize is presently disheartened in favor of more productive options like ConcurrentHashMap or Collections.synchronizedMap.

Example Code for HashMap and Hashtable:

HashMap Example:

import java.util.*;

public class HashMapExample {
public static void main(String[] args) {
HashMap<String, Integer> map = new HashMap<>();

map.put("Apple", 10);
map.put("Banana", 20);

System.out.println("HashMap: " + map);

// Retrieve value
System.out.println("Value for Apple: " + map.get("Apple"));

// Null values and keys allowed
map.put(null, 30); // Null key
map.put("Grapes", null); // Null value
System.out.println("HashMap with Nulls: " + map);
}
}

Hashtable Example:

import java.util.*;

public class HashtableExample {
public static void main(String[] args) {
Hashtable<String, Integer> table = new Hashtable<>();

table.put("Apple", 10);
table.put("Banana", 20);

System.out.println("Hashtable: " + table);

// Throws NullPointerException if null key or value is inserted
// table.put(null, 30); // Uncommenting this line will cause an exception
// table.put("Grapes", null); // Uncommenting this line will cause an exception
}
}

Difference Between HashMap and Hashtable

HashMap and Hashtable are both part of Java’s Map interface and store information in key-value pairs, but there are critical contrasts between them. Below is a nitty gritty comparison based on different aspects: