#HashSet class

[blocks2code]

HashSet Class in Java With Program Example

Set interface doesn’t provide any additional method, as a result, implementation classes use only collection interface methods. HashSet is an implementing class of Set interface and it represents Hash Table as its underlying data structure. It is a collection of unordered unique elements that don’t allow duplicates. It also doesn’t preserve insertion order as it uses hash code to store an…

[arshikasingh]

Java HashSet class

Let us learn about the Java HashSet class:

[shakshi09]

How are hashCode and equals methods related?

In Java, the hashCode() and equals() methods play a critical role in determining object equality and behavior in hash-based collections like HashMap, HashSet, and Hashtable.

The equals() method is used to compare two objects for logical equality. By default, the equals() method in the Object class compares memory references. However, in most custom classes, this method is overridden to provide meaningful comparison logic—such as comparing object content (fields) rather than memory addresses.

The hashCode() method returns an integer representation of an object’s memory address by default. However, when overriding equals(), it is essential to also override hashCode() to maintain the general contract:

If two objects are equal according to the equals() method, then they must have the same hashCode() value.

Failing to do this can lead to unexpected behavior in collections. For instance, adding two logically equal objects (via equals()) to a HashSet may result in duplicates if hashCode() returns different values for them. This is because hash-based collections first use the hashCode() to find the correct bucket, and then use equals() to compare objects within the same bucket.

Example:

@Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null || getClass() != obj.getClass()) return false; MyClass other = (MyClass) obj; return this.id == other.id; } @Override public int hashCode() { return Objects.hash(id); }

In summary, always override both methods together to ensure correct object behavior in collections. A strong grasp of these concepts is crucial for building reliable applications and is a core topic in any full stack Java developer course.

[praveennareshit]

Must-Know Core Java Concepts for Every Programmer

(A Guide for Full Stack Software Testing Enthusiasts in KPHB)

Java remains the backbone of enterprise applications, and a strong grasp of its core concepts is essential for every programmer. Whether you are an aspiring software tester, a backend developer, or a full-stack engineer, understanding Java fundamentals is non-negotiable. Let’s break down the most crucial Java concepts that you must master.

1. Object-Oriented Programming (OOP)

Java is inherently object-oriented, which means everything revolves around objects and classes. The four key pillars of OOP in Java are:

✔ Encapsulation – Bundling data and methods together to protect data integrity. ✔ Abstraction – Hiding implementation details and exposing only what’s necessary. ✔ Inheritance – Allowing one class to derive properties from another. ✔ Polymorphism – Enabling multiple implementations of a method.

Why It Matters?

For software testers, understanding OOP principles helps in creating reusable and scalable test automation frameworks.

2. Java Memory Management

Memory management is a crucial aspect that determines the performance of Java applications. It consists of:

✔ Heap & Stack Memory – Heap stores objects, while Stack holds method calls and local variables. ✔ Garbage Collection (GC) – Java has an automatic garbage collector that frees up memory by removing unused objects.

Why It Matters?

Full Stack Testers must understand memory leaks and performance bottlenecks in Java-based applications.

3. Exception Handling

Exception handling ensures that runtime errors don’t crash the application. Java provides:

✔ try-catch-finally – Handles exceptions and ensures resource cleanup. ✔ throws & throw – Used for explicitly handling custom exceptions. ✔ Checked vs. Unchecked Exceptions – Checked exceptions (like IOException) must be handled, while unchecked exceptions (like NullPointerException) occur at runtime.

Why It Matters?

Testers need to handle exceptions effectively in automation scripts to avoid script failures.

4. Multithreading & Concurrency

Multithreading allows multiple parts of a program to run simultaneously. Important concepts include:

✔ Thread Lifecycle – From creation to termination. ✔ Runnable & Callable Interfaces – Implementing threads in Java. ✔ Synchronization & Locks – Avoiding race conditions and ensuring thread safety.

Why It Matters?

In performance testing, understanding multithreading helps simulate real-world user load.

5. Collections Framework

Java provides a robust Collections Framework for handling groups of objects efficiently. The key interfaces are:

✔ List (ArrayList, LinkedList) – Ordered and allows duplicates. ✔ Set (HashSet, TreeSet) – Unordered and doesn’t allow duplicates. ✔ Map (HashMap, TreeMap) – Stores key-value pairs.

Why It Matters?

Test automation frameworks use collections extensively for data handling and assertions.

6. File Handling & I/O Operations

File handling is critical for reading, writing, and manipulating files in Java.

✔ BufferedReader & BufferedWriter – Efficient file reading and writing. ✔ FileInputStream & FileOutputStream – Handling binary data. ✔ Serialization – Converting objects into byte streams.

Why It Matters?

For automation testers, handling logs, reports, and configuration files is a routine task.

7. JDBC & Database Connectivity

Java Database Connectivity (JDBC) allows applications to interact with databases.

✔ DriverManager – Manages database connections. ✔ PreparedStatement – Prevents SQL injection. ✔ ResultSet – Retrieves query results.

Why It Matters?

Full Stack Testers should understand JDBC for validating database operations in automation scripts.

8. Java Frameworks

Mastering Java alone isn’t enough; knowing key frameworks is essential.

✔ Spring Boot – Microservices and dependency injection. ✔ Selenium with Java – Web automation testing. ✔ TestNG & JUnit – Test automation frameworks.

Why It Matters?

These frameworks power large-scale software applications and automation testing.

Frequently Asked Questions (FAQ)

Q1: What is the best way to practice Core Java concepts? A: Work on small projects, participate in coding challenges, and contribute to open-source repositories.

Q2: How is Java used in Full Stack Software Testing? A: Java is used for writing test automation scripts, interacting with databases, and integrating test frameworks.

Q3: What is the difference between Checked and Unchecked Exceptions? A: Checked exceptions must be handled (e.g., IOException), whereas unchecked exceptions occur at runtime (e.g., NullPointerException).

Q4: Why is Java preferred for automation testing? A: Java offers robust libraries like Selenium, TestNG, and JUnit, making automation testing efficient and scalable.

Q5: What are the key Java concepts needed for API Testing? A: Understanding HTTP methods, JSON parsing, and REST API calls using libraries like RestAssured and Jackson is crucial.

Final Thoughts

Mastering Java fundamentals is the key to excelling in software development and automation testing. Whether you are preparing for a Full Stack Software Testing role in KPHB or looking to enhance your coding skills, these core Java concepts will set you apart.

[sudarshannarwade]

What is the Java collection framework- 2025

The Java Collection Framework is a group of classes and interfaces that provide various data structures and algorithms for storing and manipulating data efficiently. It includes interfaces like List, Set, and Map, and implementations such as ArrayList, HashSet, and HashMap. The framework helps developers handle data more effectively, with built-in methods for searching, sorting, and modifying collections.

[subb01]

Key Concepts to Review Before Your Java Interview

Java interviews can be both challenging and rewarding, often acting as a gateway to exciting roles in software development. Whether you're applying for an entry-level position or an advanced role, being well-prepared with core concepts is essential. In this guide, we’ll cover key topics to review before your Java interview, ensuring you're confident and ready to impress. Additionally, don't forget to check out this detailed video guide to strengthen your preparation with visual explanations and code demonstrations.

1. Object-Oriented Programming (OOP) Concepts

Java is known for its robust implementation of OOP principles. Before your interview, make sure to have a firm grasp on:

Classes and Objects: Understand how to create and use objects.

Inheritance: Review how subclasses inherit from superclasses, and when to use inheritance.

Polymorphism: Know the difference between compile-time (method overloading) and runtime polymorphism (method overriding).

Abstraction and Encapsulation: Be prepared to explain how and why they are used in Java.

Interview Tip: Be ready to provide examples of how you’ve used these concepts in your projects or coding exercises.

2. Core Java Concepts

In addition to OOP, there are foundational Java topics you need to master:

Data Types and Variables: Understand primitive types (int, double, char, etc.) and how they differ from non-primitive types.

Control Structures: Revise loops (for, while, do-while), conditional statements (if-else, switch-case), and how they control program flow.

Exception Handling: Know how try, catch, finally, and custom exceptions are used to manage errors in Java.

Collections Framework: Familiarize yourself with classes such as ArrayList, HashSet, HashMap, and their interfaces (List, Set, Map).

Interview Tip: Be prepared to discuss the time and space complexities of different collection types.

3. Java Memory Management

Understanding how Java manages memory can set you apart from other candidates:

Heap vs. Stack Memory: Explain the difference and how Java allocates memory.

Garbage Collection: Understand how it works and how to manage memory leaks.

Memory Leaks: Be prepared to discuss common scenarios where memory leaks may occur and how to avoid them.

Interview Tip: You may be asked how to optimize code for better memory management or to explain how Java’s finalize() method works.

4. Multithreading and Concurrency

With modern applications requiring multi-threading for efficient performance, expect questions on:

Threads and the Runnable Interface: Know how to create and run threads.

Thread Lifecycle: Be aware of thread states and what happens during transitions (e.g., from NEW to RUNNABLE).

Synchronization and Deadlocks: Understand how to use synchronized methods and blocks to manage concurrent access, and how deadlocks occur.

Concurrency Utilities: Review tools like ExecutorService, CountDownLatch, and Semaphore.

Interview Tip: Practice writing simple programs demonstrating thread synchronization and handling race conditions.

5. Java 8 Features and Beyond

Many companies expect candidates to be familiar with Java’s evolution, especially from Java 8 onward:

Lambda Expressions: Know how to write concise code with functional programming.

Streams API: Understand how to use streams for data manipulation and processing.

Optional Class: Learn to use Optional for handling null checks effectively.

Date and Time API: Review java.time package for managing date and time operations.

Interview Tip: Be prepared to solve coding problems using Java 8 features to show you’re up-to-date with recent enhancements.

6. Design Patterns

Java interviews often include questions on how to write clean, efficient, and scalable code:

Singleton Pattern: Know how to implement and when to use it.

Factory Pattern: Understand the basics of creating objects without specifying their exact class.

Observer Pattern: Be familiar with the publish-subscribe mechanism.

Decorator and Strategy Patterns: Understand their practical uses.

Interview Tip: Have examples ready that demonstrate how you’ve used these patterns in your projects.

7. Commonly Asked Coding Problems

Prepare by solving coding problems related to:

String Manipulations: Reverse a string, find duplicates, and check for anagrams.

Array Operations: Find the largest/smallest element, rotate arrays, or merge two sorted arrays.

Linked List Questions: Implement basic operations such as reversal, detecting cycles, and finding the middle element.

Sorting and Searching Algorithms: Review quicksort, mergesort, and binary search implementations.

Interview Tip: Practice on platforms like LeetCode or HackerRank to improve your problem-solving skills under time constraints.

Final Preparation Tips

Mock Interviews: Conduct practice interviews with peers or mentors.

Review Your Code: Ensure your past projects and code snippets are polished and ready to discuss.

Brush Up on Basics: Don’t forget to revise simple concepts, as interviews can include questions on any level of difficulty.

For more in-depth preparation, watch this helpful video that provides practical examples and coding tips to boost your confidence.

With these concepts in mind, you'll be well-equipped to handle any Java interview with poise. Good luck!

[engenhariadesoftware]

Explorando HashSet em Java: Conceitos, Uso e Boas Práticas

Introdução ao HashSet O que é um HashSet? O HashSet é uma classe da biblioteca padrão do Java que implementa a interface Set, sendo parte do pacote java.util. Ele representa uma coleção que não permite elementos duplicados e não garante nenhuma ordem específica de seus elementos. O HashSet usa um mecanismo de hash para armazenar os elementos de forma eficiente, garantindo que operações como…

[vatt-world]

hi

fizzbuzz for (int i = 1; i <= 100; i++) { // Check if the number is divisible by both 3 and 5 if (i % 3 == 0 && i % 5 == 0) { System.out.println("FizzBuzz"); } // Check if the number is divisible by 3 else if (i % 3 == 0) { System.out.println("Fizz"); } // Check if the number is divisible by 5 else if (i % 5 == 0) { System.out.println("Buzz"); } // Print the number itself if it is not divisible by 3 or 5 else { System.out.println(i); } }

/// reverse string

/// implement stack class Stack { private ArrayList stackList;// Constructor to initialize the stack public Stack() { stackList = new ArrayList<>(); } // Method to push an element onto the stack public void push(int value) { stackList.add(value); } // Method to pop an element from the stack public int pop() { if (isEmpty()) { System.out.println("Stack is empty. Cannot pop."); return -1; // Return an error value, could also throw an exception } return stackList.remove(stackList.size() - 1); } // Method to peek at the top element of the stack public int peek() { if (isEmpty()) { System.out.println("Stack is empty. Cannot peek."); return -1; // Return an error value, could also throw an exception } return stackList.get(stackList.size() - 1); } // Method to check if the stack is empty public boolean isEmpty() { return stackList.isEmpty(); } // Method to get the size of the stack public int size() { return stackList.size(); }

}

public class Main { public static void main(String[] args) { Stack stack = new Stack(); stack.push(10); stack.push(20); stack.pop(); }

} \\\\\\\\

convert integer to roman numeral longest palindrome substring

///////////// design hashset

class MyHashSet { // Define the number of buckets private final int NUM_BUCKETS = 1000; // Array of LinkedLists to serve as buckets for collision handling private LinkedList[] buckets;// Constructor to initialize the buckets public MyHashSet() { buckets = new LinkedList[NUM_BUCKETS]; for (int i = 0; i < NUM_BUCKETS; i++) { buckets[i] = new LinkedList<>(); } } // Hash function to determine the index for a given key private int hash(int key) { return key % NUM_BUCKETS; } // Add a value to the HashSet public void add(int key) { int bucketIndex = hash(key); LinkedList<Integer> bucket = buckets[bucketIndex]; if (!bucket.contains(key)) { bucket.add(key); } } // Remove a value from the HashSet public void remove(int key) { int bucketIndex = hash(key); LinkedList<Integer> bucket = buckets[bucketIndex]; bucket.remove((Integer) key); // Remove the key if it exists } // Check if a value exists in the HashSet public boolean contains(int key) { int bucketIndex = hash(key); LinkedList<Integer> bucket = buckets[bucketIndex]; return bucket.contains(key); }

}

public class Main { public static void main(String[] args) { MyHashSet hashSet = new MyHashSet(); hashSet.add(1); hashSet.add(2); System.out.println(hashSet.contains(1)); // Should print true System.out.println(hashSet.contains(3)); // Should print false hashSet.add(2); System.out.println(hashSet.contains(2)); // Should print true hashSet.remove(2); System.out.println(hashSet.contains(2)); // Should print false }

}

////

Reverse Only Letters Input: s = "ab-cd" Output: "dc-ba" public class ReverseOnlyLetters { public static String reverseOnlyLetters(String s) { // Convert the input string to a character array char[] chars = s.toCharArray(); int left = 0; // Initialize the left pointer int right = s.length() - 1; // Initialize the right pointer while (left < right) { // Move left pointer until it finds a letter while (left < right && !Character.isLetter(chars[left])) { left++; } // Move right pointer until it finds a letter while (left < right && !Character.isLetter(chars[right])) { right--; } // Swap the letters at the left and right pointers char temp = chars[left]; chars[left] = chars[right]; chars[right] = temp; // Move the pointers towards each other left++; right--; } // Convert the character array back to a string return new String(chars); } public static void main(String[] args) { String s = "ab-cd"; System.out.println(reverseOnlyLetters(s)); // Output: "dc-ba" }

}

///

Java group by sort – multiple comparators example

/// SELECT Owner FROM Account WHERE Balance >= 10000 AND ExpirationDate BETWEEN '2017-04-20' AND '2017-04-22'

///

SELECT *

FROM CITY

WHERE COUNTRYCODE = 'USA' AND POPULATION > 100000;

////

Write a simple lambda in Java to transpose a list of strings long value to a list of long reversed. Input: [“1”,”2”,”3”,”4”,”5”] output: [5,4,3,2,1]

///////////////

2. Write a Java Program to count the number of words in a string using HashMap.

Sample String str = "Am I A Doing the the coding exercise Am"

///////////////

Write a simple lambda in Java to transpose a list of strings long value to a list of long reversed. Input: [“1”,”2”,”3”,”4”,”5”] output: [5,4,3,2,1]

//////////

Customer :

CustomerId : int Name : varchar(255)

Account :

AccountId : int CustomerId : int AccountNumber : varchar(255) Balance : int

Transactions :  Transactionid : int AccountId: int TransTimestamp : numeric(19,0) Description : varchar(255) Amount(numeric(19,4))   3. Write a select query to find the most recent 10 transactions.

//////////// 4. Write a select query, which, given an customer id, returns all the transactions of that customer.

///////////// 5. What indexes should be created for the above to run efficiently? CustomerId, AccountId

///////////

6. Write a program to sort and ArrayList.

ArrayList list = new ArrayList<>(); list.add("Banana"); list.add("Apple"); list.add("Orange"); list.add("Mango"); // Print the original ArrayList System.out.println("Original ArrayList: " + list); // Sort the ArrayList in natural order Collections.sort(list); // Print the sorted ArrayList System.out.println("Sorted ArrayList: " + list);

[dosomedev]

Youtube Video Ideas

I want to post videos about the Java basics of: - Stack - ArrayDeque - HashMap - HashSet - LinkedHashMap - LinkedHashSet - TreeMap - TreeSet - IdentityHashMap

Do you have any ideas for more content? Any other Java class I should dive into?

My Channel: youtube.com/@DoSomeDev

[roseliejack123]

Mastering Java: Key Concepts and Skills Every Developer Should Know

Java has long been a cornerstone in the world of programming, known for its robustness and versatility. Whether you're just starting out or looking to enhance your existing skills, understanding the fundamental aspects of Java is crucial.

Enrolling in a Java Course in Pune significantly enhances one's ability to leverage Java's capabilities effectively. Understanding its primary advantages is crucial for developers and businesses considering its adoption.

In this blog, we'll walk through the essential elements of Java programming and why they're important for your development journey.

1. Understanding Java Basics

Variables and Data Types At the core of Java programming are variables and data types. Get to know the basic types like int, double, char, and boolean, and learn how to effectively declare and initialize variables. These are the building blocks of your Java applications.

Operators Java offers a variety of operators to perform operations on data. From arithmetic and relational to logical and bitwise operators, mastering these will allow you to manipulate and evaluate data in your programs.

Control Flow Statements Control flow is key to creating dynamic programs. Learn how to use if-else statements, switch cases, and conditional operators to control the execution of your code based on various conditions.

2. Core Object-Oriented Concepts

Classes and Objects Java is fundamentally object-oriented. Understand how to define classes and create objects, and get comfortable with constructors, fields, and methods. This is essential for structuring and organizing your code.

Inheritance Inheritance allows you to create new classes based on existing ones. Learn how to extend classes and override methods to build upon existing functionality and create specialized classes.

Polymorphism Polymorphism in Java enables you to use a single interface for multiple implementations. Study method overloading (multiple methods with the same name but different parameters) and method overriding (redefining methods in subclasses) to make your code more flexible and reusable.

Encapsulation Encapsulation involves wrapping data and methods into a single unit, or class, and restricting access to some of the object's components. Learn to use access modifiers (private, protected, public) and getter/setter methods to protect your data and enhance code maintainability.

Abstraction Abstraction allows you to define abstract classes and interfaces to represent common behaviors. This concept helps in designing more flexible and scalable systems by hiding implementation details.

Consider enrolling in the Java Online Certification Training to fully harness Java's capabilities and become proficient in web automation.

3. Exploring Core Java Features

String Handling Strings are a fundamental part of Java. Master the String class and its methods for string manipulation, comparison, and formatting to handle textual data efficiently.

Collections Framework Java's Collections Framework provides a set of interfaces and classes for managing groups of objects. Get familiar with ArrayList, HashSet, HashMap, and other collections to handle data in various ways.

Exception Handling Robust exception handling is crucial for maintaining application stability. Learn how to use try, catch, finally, and custom exceptions to gracefully handle errors and unexpected situations.

File and I/O Operations Handling file input and output is essential for many applications. Learn how to use classes from java.io and java.nio.file to read from and write to files, manage data, and handle file-related operations.

4. Advanced Java Topics

Multithreading Multithreading allows you to perform multiple tasks concurrently. Understand how to create and manage threads and learn about synchronization to ensure your application runs smoothly when dealing with concurrent processes.

Streams API The Stream API in Java provides a functional approach to processing sequences of data. Learn how to use streams for operations like filtering, mapping, and reducing to write concise and readable code.

Lambda Expressions Lambda expressions enable you to write more compact and expressive code. Study how to use lambda expressions with functional interfaces to simplify your code and improve its readability.

Networking Java provides powerful networking capabilities for building networked applications. Get to know the basics of socket programming to create server and client applications that communicate over a network.

5. Utilizing Java APIs and Libraries

Java Standard Library The Java Standard Library offers a wealth of built-in classes and methods. Explore libraries such as java.lang, java.util, java.io, and java.nio to take advantage of pre-built functionality.

Java EE (Enterprise Edition) For enterprise-level applications, familiarize yourself with Java EE technologies like servlets, JavaServer Pages (JSP), and Enterprise JavaBeans (EJB). These technologies are essential for building scalable and robust enterprise solutions.

6. Effective Development Practices

Integrated Development Environments (IDEs) IDEs like Eclipse, IntelliJ IDEA, and NetBeans provide powerful tools for coding, debugging, and managing Java projects. Learn to navigate these environments to enhance your productivity and development efficiency.

Build Tools Tools such as Maven and Gradle help manage project dependencies and automate the build process. Mastering these tools will streamline your development workflow and simplify project management.

Version Control Version control systems, particularly Git, are essential for tracking changes and collaborating on code. Understanding version control will help you manage your codebase effectively and work seamlessly with other developers.

7. Testing and Debugging

Unit Testing Unit testing frameworks like JUnit and TestNG are crucial for verifying that your code works as intended. Learn how to write and run unit tests to ensure the correctness of your code.

Debugging Debugging skills are vital for identifying and resolving issues in your code. Get to know the debugging tools available in your IDE to troubleshoot and fix problems efficiently.

8. Understanding the Java Virtual Machine (JVM)

JVM Basics The Java Virtual Machine plays a crucial role in executing Java programs. Learn about bytecode and the JVM memory model to understand how Java applications are run and managed.

Garbage Collection Java’s garbage collection mechanism helps manage memory automatically. Understand how garbage collection works to optimize memory usage and improve application performance.

9. Adopting Java Best Practices

Coding Conventions Following Java coding conventions ensures that your code is clean, readable, and maintainable. Adhering to best practices will help you write high-quality code that is easy to understand and manage.

Design Patterns Design patterns like Singleton, Factory, and Observer provide proven solutions to common problems. Familiarize yourself with these patterns to design effective and reusable software.

Conclusion

Becoming proficient in Java involves mastering its core concepts, advanced features, and best practices. By understanding the basics, diving into object-oriented programming, and exploring advanced topics like multithreading and networking, you'll be well-equipped to develop robust Java applications. Embrace these fundamental aspects of Java, and you'll be on your way to becoming a skilled Java developer.

[tpointtech12]

The Ultimate Guide to Java Collection

Java libraries are indispensable tools that streamline development by providing pre-written code for common tasks. "The Ultimate Guide to Java Libraries" explores a myriad of libraries that enhance Java programming, from handling data structures to implementing complex algorithms.

A key feature covered is collections in Java, which offer efficient ways to manage groups of objects, improving code efficiency and readability.

TpointTech is a valuable resource for developers seeking in-depth tutorials and examples on using these libraries effectively. Leveraging these libraries can significantly reduce development time and improve application performance.

Overview of Java Collections

The Java Collections Framework includes interfaces, implementations, and algorithms. The core interfaces include Collection, List, Set, Queue, and Map, each serving different purposes.

Collection Interface: 

The root interface of the framework, representing a group of objects known as elements. It is extended by List, Set, and Queue interfaces.

List Interface: 

An ordered collection that allows duplicate elements. Common implementations are ArrayList, LinkedList, and Vector. Lists are ideal when you need to access elements by their index.

ArrayList: Resizable array implementation, offering constant-time positional access but slower for insertion and deletion.

LinkedList: Doubly-linked list implementation, providing efficient insertion and deletion but slower access time.

Vector: Synchronized version of ArrayList, rarely used due to performance overhead.

Set Interface: 

A collection that does not allow duplicate elements. It models mathematical sets and provides implementations like HashSet, LinkedHashSet, and TreeSet.

HashSet: Uses a hash table for storage, offering constant-time performance for basic operations.

LinkedHashSet: Maintains insertion order, slightly slower than HashSet.

TreeSet: Implements the SortedSet interface, ensuring elements are in ascending order, based on their natural ordering or a specified comparator.

Queue Interface: 

Designed for holding elements prior to processing, typically ordered in a FIFO (first-in-first-out) manner. Common implementations include LinkedList, PriorityQueue, and ArrayDeque.

PriorityQueue: Elements are ordered according to their natural ordering or a provided comparator, useful for creating priority-based tasks.

ArrayDeque: Resizable-array implementation of the Deque interface, providing efficient insertion and deletion from both ends.

Map Interface: 

Represents a collection of key-value pairs, where each key maps to one value. Popular implementations are HashMap, LinkedHashMap, and TreeMap.

HashMap: Provides constant-time performance for basic operations, assuming a good hash function.

LinkedHashMap: Maintains a doubly-linked list of its entries, preserving the order of insertion.

TreeMap: Implements the SortedMap interface, ensuring keys are in ascending order.

Advantages of Java Collections Framework

Reduces Programming Effort: With a set of ready-made data structures and algorithms, JCF eliminates the need for developers to implement complex data structures from scratch.

Increases Program Speed and Quality: Standardized interfaces and optimized implementations ensure high performance and reliability.

Interoperability: Collections can be easily passed across APIs, reducing the complexity of integration.

Ease of Maintenance: Well-documented and widely-used classes make it easier for developers to maintain and enhance code.

Common Algorithms in JCF

Java Collections Framework includes various algorithms to perform routine tasks, such as sorting, searching, and shuffling. These algorithms are static methods in the Collections utility class.

Sorting: Collections.sort(List list), sorts the specified list into ascending order.

Shuffling: Collections.shuffle(List list), randomly permutes the elements in the list.

Searching: Collections.binarySearch(List> list, T key), performs binary search on a sorted list.

Conclusion

The Java Collections Framework is indispensable for any Java developer. It offers a standardized and efficient way to manage groups of objects, making code more robust and maintainable.

By leveraging the various interfaces and implementations, such as lists, sets, queues, and maps, developers can handle data structures effectively.

Understanding collections in Java, as detailed on resources like TpointTech, is crucial for building high-performance applications. Whether you're a beginner or an experienced developer, mastering Java collections will significantly enhance your programming capabilities.

[vibinjack]

Java Topics Demystified: Everything You Need To Know

Introduction:

Java, a stalwart in the programming world, is a cornerstone for developers due to its robustness, versatility, and platform independence. For beginners and seasoned programmers alike, understanding the core topics in Java can significantly enhance one's ability to create efficient and maintainable code. This article demystifies essential Java topics, providing a comprehensive overview to guide your learning journey. Enrolling in in-depth Java Training In Chennai is a great way for anyone looking to improve their programming abilities to get real-world experience and knowledge relevant to the business.

Object-Oriented Programming (OOP)

At the heart of Java lies Object-Oriented Programming (OOP), a paradigm that organizes software design around data or objects rather than functions and logic. The four fundamental principles of OOP in Java are:

Encapsulation: This is grouping variables (data) and functions (methods) that manipulate the data into a class unit. Encapsulation helps protect data from unauthorised access and modification.

Inheritance: Java allows a class to inherit the properties and methods of another class. This promotes code reuse and establishes a natural hierarchical relationship between classes. For example, a `Car` class can be inherited from a `Vehicle` class.

Polymorphism: Polymorphism enables objects to be treated as instances of their parent class rather than their actual class. The two types of polymorphism in Java are compile-time (method overloading) and runtime (method overriding).

Abstraction: According to this concept, only the object's most important features should be displayed, concealing the intricate implementation details. Java achieves abstraction through the usage of abstract classes and interfaces. 

Data Structures And Collections

The Java Collections Framework (JCF) is the aggregate name for Java's extensive collection of built-in data structures. Understanding these data structures is crucial for effective programming.

- List: an arranged grouping that may include duplicate items. Common implementations include `LinkedList` and `ArrayList` classes. 

- Set: A collection that does not allow duplicate elements. The `HashSet` and `TreeSet` classes are popular choices.

- Map: a mapping object that prevents duplicate keys and associates keys with values. The implementations `HashMap} and `TreeMap} are commonly used. 

These structures help manage and organise data efficiently, enabling faster retrieval and manipulation.

Exception Handling

Exception handling is a technique to manage runtime problems and maintain the program's normal flow. Java provides five keywords for exception handling:

- try: To specify a block of code to be tested for errors.

- catch: To handle the exception if it occurs.

- throw: To explicitly throw an exception.

- throws: To declare an exception that might be thrown by a method.

Proper exception handling makes your code more robust and error-resistant.

Concurrency

Concurrency in Java is achieved through multithreading, where multiple threads run concurrently within a program. Key concepts include:

- Thread Class: Extending the `Thread` class to create a new thread.

- Runnable Interface: Implementing the `Runnable` interface to define the code executed by the thread.

- Synchronisation: Managing the access of multiple threads to shared resources to prevent data inconsistency.

Understanding concurrency is vital for writing efficient, high-performance applications.

Java Development Tools

Mastering Java involves familiarity with development tools and environments that streamline coding, debugging, and deployment processes. Notable tools include:

- Integrated Development Environments (IDEs): Eclipse, IntelliJ IDEA, and NetBeans offer comprehensive support for Java development.

- Build Tools: Maven and Gradle automate project build, dependency management, and more.

- Version Control Systems: Git is essential for collaborative development and version tracking.

- If you want to enhance your programming skills, enrolling in a reputable Software Training Institute In Chennai can provide you with the necessary knowledge and hands-on experience.

Conclusion:

Java's vast ecosystem offers many features that cater to various programming needs. By mastering OOP principles, data structures, exception handling, concurrency, and essential development tools, you can harness the full potential of Java to build robust, scalable, and efficient applications. Maintaining proficiency in this dynamic language requires constant study and practice, whether a beginner or an expert.

[arshikasingh]

Constructors of Java HashSet Class

Let us see the Constructors of Java HashSet Class:

[bitesizedcode]

Leetcode 36. Sudoku Solver:

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Each row must contain the digits 1-9 without repetition.

Each column must contain the digits 1-9 without repetition.

Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.

Solution follows in c#, algorithm from neetcode.io

public class Solution {

public bool IsValidSudoku(char[][] board) {

Dictionary<int,HashSet<char>> cols = new Dictionary<int,HashSet<char>>(9); Dictionary<(int,int),HashSet<char>> sqrs = new Dictionary<(int,int),HashSet<char>>(9);

for(int r = 0; r<9; r++){

rows.TryAdd(r,new HashSet<char>());

}

cols.TryAdd(r,new HashSet<char>());

}

for(int a = 0; a < 3; a++){

for(int b = 0; b < 3; b++){

sqrs.TryAdd((a,b),new HashSet<char>());

}

for(int r = 0; r<9; r++){

for(int c = 0; c<9; c++){

if(board[r][c] == '.'){

continue;

}

if(rows[r].Add(board[r][c]) &&

cols[c].Add(board[r][c]) &&

sqrs[(r/3,c/3)].Add(board[r][c]) ){

continue;

}else{

return false;

}

}

}

return true;

}

}

[some-programming-pearls]

Write a sample Java 17 program to find the first repeat element/character from a given string by Java Streams. Explain the steps followed.

Here’s a Java 17 sample program to find the first repeated element or character from a given string using Java Streams: import java.util.HashSet; import java.util.Optional; public class FirstRepeatElement { public static void main(String[] args) { String input = "programming"; Optional<Character> firstRepeated = input.chars() .mapToObj(c -> (char) c) .collect(HashSet::new, (set, ch) -> { if…

[full-stack-development21]

Unraveling the Power of Java Collections Framework and Interfaces

In the realm of Java programming, understanding the intricacies of the Java Collections Framework and Interfaces is pivotal for building robust and efficient applications. Let's delve into the essentials, including Java PriorityQueue and sets in Java, to harness the full potential of these foundational components.

Java Collections Framework: A Comprehensive Toolbox

The Java Collections Framework is a powerhouse of data structures and algorithms, offering a versatile toolbox for developers. It provides interfaces and classes for managing and manipulating groups of objects, ensuring flexibility and efficiency in Java programming.

Java Interfaces: Enabling Polymorphism and Abstraction

Java Interfaces play a crucial role in achieving polymorphism and abstraction in programming. By defining a set of methods that implementing classes must adhere to, interfaces allow developers to create flexible and interchangeable components within their codebase.

Java PriorityQueue: Prioritizing Efficiency

Java PriorityQueue, a class within the Collections Framework, stands out as a specialized queue implementation. It orders elements based on their natural ordering or according to a specified comparator, enabling developers to prioritize and efficiently manage tasks in their applications.

Sets in Java: Uniqueness and Order

Sets in Java, a part of the Collections Framework, ensure uniqueness of elements within a collection. Whether using HashSet, TreeSet, or LinkedHashSet, developers can leverage sets to manage distinct elements and, in some cases, maintain a specific order.

Conclusion: Elevating Java Programming Proficiency

Mastering the Java Collections Framework, Java Interfaces, PriorityQueue, and sets in Java empowers developers to create scalable and well-organized applications. These foundational concepts not only streamline data management but also enhance the overall efficiency and maintainability of Java code. As you explore these elements, you unlock the potential to elevate your proficiency in Java programming, creating more robust and sophisticated software solutions.