Hashmap vs hashtable

While the Hashtable was part of the initial Java release over two decades ago, the HashMap is the correct key-value store to use today. When HashMap vs. Hashtable differences One key HashMap vs. Hashtable difference is the fact that the older component is synchronized, which means concurrent access to the Hashtable’s underlying collection isn't allowed. Method locks limit access to one thread at a time. On the surface, this sounds like a benefit, but it’s not. A drawback to synchronization is that it’s costly in terms of performance. However, it's unlikely that the performance difference between a HashMap and Hashtable will ever be of any consequence for a traditional enterprise application. Network latency and database connections typically act as a much larger performance bottleneck than A concurrent application shouldn't rely on the underlying collection class to mitigate synchronized access to its content. Instead, the application should write its own synchronized methods to coordinate threads. If the application controls the synchronization, the underlying Hashtable or HashMap won't need to. The best practice is to synchronize only when needed. The HashMap promotes this programming paradigm while the Hashtable performs synchronization even when it's not necessary. How to synchronize a HashMap What if a developer needs constant, low-level synchronization at the class level? It's still not a justification to choose a Hashtable. A developer can create a synchronized Hash...

At an entry-level, one of the most frequently asked key and values. So, this article will help you know the major differences between these two. I’ll be discussing the topics in the following order: • • • • Let’s begin! What is HashMap? Key. It is termed as HashMap because it uses a technique called Hashing. Hashing is a process of converting a large What is a Hashtable? A Hashtable is a Java Hashtable class implements a hashtable, that maps keys to values. It inherits the Dictionary class and implements the Map interface. Hashtable Declaration publicclassHashtableextendsDictionaryimplementsMap,Cloneable,Serializable K: It is the type of keys that by the map. V: This is the type of mapped values. Now that you guys have understood how HashMap and Hashtable in Java works, let’s take a look at the parameters to understand the differences between HashMap and Hashtable. Now let’s point out the major differences between HashMap and Hashtable. Java HashMap vs Hashtable Parameters HashMap Hashtable Synchronization Non-synchronized meaning that it is not thread-safe and cannot be shared between many threads without a proper synchronization code. Synchronized and can be shared with many threads Null keys Allows only one null key and multiple null values Does not allow null key or its value Legacy System This is a part of Java Collections Hashtable is a legacy class was not part of the initial Iterator Iterator is fail-fast and it throws a concurrentModificationException if any other...

• It is kind of like HashMap but is synchronized. • Hashtable stores key/value pair in the hash table. • In Hashtable we specify an object that is used as a key, and the value we want to associate with that key. The key is then hashed, and the resulting hash code is used as the index at which the value is stored within the table. • The initial default capacity of Hashtable class is 11 whereas load Factor is 0.75. • HashMap doesn’t provide any Enumeration, while Hashtable provides not fail-fast Enumeration. Example: 4 Mona Lisa 3 Joe Biden 2 Donald Trumph 1 James Bond SynchronizedHashMap • Synchronization at the Object level. • Every read/write operation needs to acquire lock. • Locking the whole collection is a performance overhead. • This essentially gives access to just one thread to the entire map & blocks all the other threads. • It may cause contention. • Example: 1: Brad 2: Anil 4: Sachin 88: XYZ 44: Ajit Hashtable vs SynchronizedHashMap Hashtable Synchronized HashMap Hashtable doesn’t allow even a single null key and null values. Synchronized HashMap allows one null key and any number of null values. Iterators returned by Hashtable are fail-safe in nature. i.e they don’t throw ConcurrentModificationException if the map is modified after the creation of the iterator. Iterators returned by synchronized HashMap are fail-fast in nature. i.e they throw ConcurrentModificationException if the map is modified after the creation of iterator. HashTable was there since J...

Hash tables are a fundamental data structure used in computer science to implement dictionaries, associative arrays, and sets. In Java, the two most commonly used hash table implementations are the HashMap and HashTable classes. Both classes provide similar functionality, but they differ in their performance characteristics, thread-safety, and feature set In this blog post, we will explore the functional and performance differences between Java’s HashMap and HashTable classes. Functional Differences The functional differences between HashMap and HashTable are relatively minor, but they can be significant depending on your use case. • Thread-Safety The most significant difference between HashMap and HashTable is that HashTable is thread-safe, while HashMap is not. HashTable provides synchronized methods to ensure that only one thread can modify the table at a time. On the other hand, HashMap is not synchronized, which means that multiple threads can modify the table simultaneously, leading to data corruption and unpredictable behavior. • Null Keys and Values HashTable does not allow null keys or values. Any attempt to store a null key or value will result in a NullPointerException. In contrast, HashMap allows null keys and values, making it more flexible in some cases. • Iteration Order The iteration order of HashMap is not guaranteed and can change over time as elements are added or removed. In contrast, HashTable guarantees a predictable iteration order based on the order...

Table of Contents • • • • • • • • Introduction Often Java HashMap is mistaken for HashTable by developers and server designers and vice-versa, the two terms are distinct and have an extensively broad meaning. Although the origin of HashMap is the same as that of HashTable, yet there is a wide chain of differences between the two. First, let’s understand the meaning of the two terms and their implications individually, then we shall discuss their difference on various bases to get more clarity on Java HashMap vs HashTable. What is HashMap? HashMap is a Map-based collection class in Java that is used for storing data in key-value pairs. It assists us in implementing the Map interface in It is called so, as it uses a technique known as Hashing. Hashing is a process of converting one large string to a smaller one by keeping its value constant. The resulting compressed value is used for indexing and running quick queries. Image Source: deepakvadgama.com What is HashTable? Hashtable is a widely used In Java, a hashtable is implemented by the Hashtable class which maps the keys to the values. It inherits the Image Source: Wikipedia Declaration of a Hash Table: public class Hashtable extends Dictionary implements Map, Cloneable, Serializable K: It is the type of keys that are on the map. V: This is the type of mapped values. Similarities Between HashMap Vs Hashtable 1. Insertion Order:HashMap and Hashtable do not assure that the order of the map will remain constant at all instanc...

Hashtable and Hashmap are two commonly used data structures in Java that allow efficient storage and retrieval of key-value pairs. While they share similar functionalities, there are some notable differences between them that developers should be aware of when choosing between them for their Java applications. In this article, we will explore the differences between Hashtable and Hashmap in Java, including their performance, synchronization, and usage scenarios. By the end of this article, you will have a clear understanding of Hashtable Vs Hashmap and be able to make an informed decision on which one to use for your specific use case. HashMap and Hashtable Overview Now we will try to understand what are HashMap and Hashtable in java. HashMap in Java A HashMap is an implementation of the Map interface in Java. It allows you to store and retrieve key-value pairs in a way that is optimized for fast lookup of values based on their keys. HashMap uses a hash table data structure to store the key-value pairs, where each key is hashed and the corresponding value is stored in the hash table based on its hash code. ALSO READ: Java string method explained [Easy Examples] HashMap is not synchronized by default, which means that it is not thread-safe. This means that if multiple threads access a HashMap simultaneously, it can result in undefined behavior, including data corruption and inconsistent results. However, you can make a HashMap thread-safe by using the ConcurrentHashMap clas...