Posted on Jun 30 • Originally published at Medium Hashing is a fundamental concept in computer science and plays a crucial role in efficient data storage and retrieval. In this blog post, we will explore hashing in the context of Java programming language, focusing on two important classes: HashMap and HashSet. We'll cover the basics of hashing, explain the purpose and usage of HashMap and HashSet, provide Java syntax examples, showcase practical use cases, and discuss problem-solving patterns. So let's dive in!Hashing is a technique used to map data to a fixed-size value, known as a hash code or hash. It takes an input, performs some calculations on it, and produces a unique hash code. The resulting hash code is used as an index or key to store or retrieve data in a data structure.HashMap is a class in Java's Collections framework that implements the Map interface. It provides a way to store key-value pairs, where each key is unique. The keys are hashed to generate hash codes, which are then used to index and store the corresponding values. HashMap allows for efficient retrieval and modification of data.To create a HashMap in Java, you need to import the java.util.HashMap class. Here's the syntax for creating a HashMap:The KeyType represents the data type of the keys, and ValueType represents the data type of the values.Let's consider an example where we store the ages of individuals using their names as keys in a HashMap:In this example, we create a HashMap ageMap with keys of type String and values of type Integer. We store the ages of three individuals and retrieve Alice's age using her name as the key.HashSet is another class in Java's Collections framework that implements the Set interface. It represents a collection of unique elements where the order is not important. HashSet uses hashing internally to store and retrieve elements efficiently.To create a HashSet in Java, you need to import the java.util.HashSet class. Here's the syntax:The ElementType represents the data type of the elements in the set.Let's consider an example where we store a list of unique names using a HashSet:In this example, we create a HashSet nameSet with elements of type String. We add three unique names and check if "Alice" exists in the set using the contains() method.a cache mechanism, where expensive calculations or database queries can be stored and retrieved quickly using unique keys.Hashing is a powerful technique that enables efficient storage and retrieval of data in Java. HashMap and HashSet are two essential classes that leverage hashing to provide key-value mapping and store unique elements, respectively. By understanding the concepts, syntax, practical use cases, important methods, and problem-solving patterns of HashMap and HashSet, you'll have a solid foundation to leverage these classes effectively in your Java projects.Basics of DS Algo Blogs:1. Hashing in JavaRecommended YouTubers for LeetCode Problems:1. NeetCode2. Take U ForwardFree Resources for Learning Data Structures and Algorithms:1. NeetCode Roadmap2. Striver’s SDE SheetRecommended Courses for Learning Data Structures and Algorithms:Top Coursera Courses for Learning Data Structures and Algorithms:(Note: The Coursera courses can be audited to get free access to the lectures)Who Am I?I’m Aswin Barath, a Software Engineering Nerd who loves building Web Applications, now sharing my knowledge through Blogging during the busy time of my freelancing work life. Here’s the link to all of my craziness categorized by platforms under one place: https://linktr.ee/AswinBarath🎙 Disclosure: Please note that some of the links mentioned on this page may be affiliate links. This means that if you click on one of these links and make a purchase, I may earn a small commission from the sale.Keep LearningNow, I guess this is where I say goodbye 👋. But, hey it’s time for you to start learning with your newfound Knowledge(Power)👨‍💻👩‍💻. Good Job that you made it this far 👏 & Thank you so much for reading my Blog 🙂.Templates let you quickly answer FAQs or store snippets for re-use. Are you sure you want to hide this comment? It will become hidden in your post, but will still be visible via the comment's permalink. 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