#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:

[vatt-world]

hi

import java.util.HashMap; import java.util.Map;

public class FrequencyCounter { public static void main(String[] args) { int[] nums = {2, 3, 2, 5, 3, 2}; Map<Integer, Integer> frequencyMap = new HashMap<>(); for (int num : nums) { frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1); } // Print the result for (Map.Entry<Integer, Integer> entry : frequencyMap.entrySet()) { System.out.println("Number " + entry.getKey() + " appears " + entry.getValue() + " times."); } }

} ////////////////////

rray = [2, 1, 5, 1, 3, 2] target = 8 We’ll find the longest subarray where the sum is ≤ 8.

We use left, right, and sum to control and track the window .int left = 0, sum = 0, max = 0;

left: starting point of our sliding window

sum: running total of the current window

count: total number of valid subarrays we find

for (int right = 0; right < array.length; right++) { Expands the window by moving the right pointer forward. sum += array[right]; while (sum > target) { sum -= array[left]; left++; } max = Math.max(max, right - left + 1); }

/// Inheritance Inheritance allows a class to inherit fields and methods from another class. It supports code reuse and method overriding.

🔹 10. Polymorphism Polymorphism lets you perform the same action in different ways. It includes compile-time (overloading) and runtime (overriding) polymorphism.

🔹 11. Encapsulation Encapsulation binds data and methods together, hiding internal details. It’s achieved using private fields and public getters/setters.

🔹 12. Abstraction Abstraction hides complex implementation details and shows only the essentials. It’s achieved using abstract classes or interfaces.

List allows duplicates, Set allows only unique elements, Map stores key-value pairs. They are part of the Java Collections Framework f

Lambdas enable functional-style code using concise syntax. They simplify the implementation of functional interfaces.

🔹 19. Functional Interfaces A functional interface has exactly one abstract method. Examples include Runnable, Callable, and Comparator.

Stream API processes collections in a functional and pipeline-based way. It supports operations like filter(), map(), and collect()

Heap stores objects and is shared, while Stack stores method calls and local variables. Stack is thread-safe; Heap is managed by the garbage collector.

Immutable objects, like String, cannot be changed once created. They are thread-safe and useful in concurrent applications.

int left = 0, right = array.length - 1; while (left < right) { if (array[left] + array[right] == target) { // Found pair } else if (array[left] + array[right] < target) { left++; } else { right--; } } //////////////////

kafka partitions

List inputList = // input data Map uniqueMap = new HashMap<>();

for (Person person : inputList) { String key = person.name + "_" + person.age;if (!uniqueMap.containsKey(key)) { uniqueMap.put(key, person); // first time seeing this name+age } else {

///

List people = Arrays.asList( new Person("Alice", 30), new Person("Bob", 25), new Person("Charlie", 35) ); // Sort by age using lambda people.sort((p1, p2) -> Integer.compare(p1.getAge(), p2.getAge()));

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

public Person(String name, int age) { this.name = name; this.age = age; }@Override public boolean equals(Object o) { if (this == o) return true; if (!(o instanceof Person)) return false; Person person = (Person) o; return age == person.age && Objects.equals(name, person.name); } @Override public int hashCode() { return Objects.hash(name, age); }

}

/////////// hashCode() is used by hash-based collections like HashMap, HashSet, and Hashtable to find the bucket where the object should be placed.

bject.equals() method compares memory addresses

///

List people = Arrays.asList( new Person("Alice", 30), new Person("Bob", 25), new Person("Charlie", 35) ); // Sort by age using lambda people.sort((p1, p2) -> Integer.compare(p1.getAge(), p2.getAge())); // Print sorted list people.forEach(System.out::println); }

///

[lakshmimonopoly1]

Mastering Java: Key Concepts for Intermediate and Advanced Learners

If you're enrolled in java full stack training in Hyderabad, it's important to move beyond the basics and explore Java’s more advanced features. Mastering these key concepts will help you build strong, efficient, and professional applications that meet real-world industry demands.

1. Deep Understanding of OOP (Object-Oriented Programming)

Java is built on OOP principles. At the intermediate and advanced levels, you should know how to apply:

Abstraction –  A class or interface can be abstracted to hide implementation details.

Encapsulation – protecting data by making variables private and using getter/setter methods.

Inheritance – allowing one class to inherit from another to reuse code.

Polymorphism – writing one method that behaves differently based on object type.

2. Exception Handling and Generics

Good Java developers write code that handles errors gracefully. You should be able to:

Use try-catch-finally blocks and create custom exceptions.

Work with Generics to make your code more flexible and type-safe, especially when dealing with collections.

3. Collections and Stream API

Java’s Collections Framework (like ArrayList, HashMap, HashSet) is essential for handling data. With Streams and Lambda expressions, you can process data more efficiently and write shorter, cleaner code.

4. Multithreading and Concurrency

Advanced Java includes running multiple tasks at the same time (multithreading). Java provides tools like Thread, ExecutorService, and Future to build responsive and scalable applications.

Conclusion

Mastering these core concepts is essential to becoming a Java developer. If you're looking for expert guidance and hands-on training, Monopoly IT Solutions Pvt. Ltd. offers the best industry-focused programs in Hyderabad to help you grow your Java career with confidence.

[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…

[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

[arshikasingh]

Constructors of Java HashSet Class

Let us see the Constructors of Java HashSet Class:

[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);

[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.

[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.