Java Data Structures: Linked List, Stack, Queue, and More

**Polymorphism**: Allows a parent class reference to point to child objects, promoting flexibility in handling objects. - **Dynamic Method Dispatch**: Java determines the method at runtime based on the object\'s type, enabling method overriding. **Inheritance**: A class derives properties an...

**Polymorphism**: Allows a parent class reference to point to child objects, promoting flexibility in handling objects. - **Dynamic Method Dispatch**: Java determines the method at runtime based on the object\'s type, enabling method overriding. **Inheritance**: A class derives properties and behaviors from another class using the extends keyword, creating a hierarchy. - **Super Keyword**: Allows access to the parent class\'s members. **Encapsulation**: Combines data (fields) and methods in a single unit, usually a class. - **Access Modifiers**: Use private for fields and public for getter/setter methods to control access. **Abstraction**: Focuses on what an object does rather than how it does it, implemented via abstract classes and interfaces. - **Abstract Classes and Interfaces**: Define methods that subclasses must implement, using abstract keyword. **Dependency, Association, Aggregation, and Composition**: - **Dependency**: A class uses another class, often seen in method parameters. - **Association**: Loose relationship where classes are aware of each other but independently exist. - **Aggregation**: \"Has-a\" relationship, where one class contains another without ownership (e.g., Library and Book). - **Composition**: Stronger aggregation where one class owns the other (e.g., Engine and Car). **Data Structures in Java** **1. Linked List (Java LinkedList Class)** Java's LinkedList class supports various methods to add, remove, and manage nodes: - **Adding Elements**: -.addFirst(element): Inserts an element at the beginning. -.addLast(element) or.add(element): Inserts at the end. -.add(index, element): Inserts at a specific position. - **Removing Elements**: -.removeFirst(): Removes the first element. -.removeLast(): Removes the last element. -.remove(index) or.remove(element): Removes by index or by element value. - **Accessing Elements**: -.get(index): Returns the element at a specific index. -.getFirst() and.getLast(): Retrieves first or last element. **2. Stack (Java Stack Class)** A LIFO (Last-In-First-Out) data structure: - **Adding Elements**:.push(element) adds an element to the top of the stack. - **Removing Elements**:.pop() removes and returns the top element. - **Accessing the Top**:.peek() retrieves the top element without removing it. - **Checking for Empty Stack**:.empty() returns true if the stack is empty. **3. Queue (Java Queue Interface with LinkedList or ArrayDeque Implementation)** A FIFO (First-In-First-Out) structure, commonly implemented with LinkedList: - **Adding Elements**: -.add(element) or.offer(element): Adds to the end;.offer() returns false if the queue is full. - **Removing Elements**: -.remove() or.poll(): Removes and returns the front element;.poll() returns null if empty. - **Accessing Elements**: -.element() or.peek(): Retrieves the front element without removal. **4. Binary Tree (Custom Implementation)** Java does not have a built-in binary tree, so it's typically implemented using a custom Node class: - **Node Structure**: A Node class typically has data, left, and right attributes. - **Adding Nodes**: - **Binary Search Tree (BST)**: Start at the root, adding nodes by comparing values (smaller to the left, larger to the right). - **Removing Nodes**: - **Leaf Node**: Set the parent's link to null. - **Node with One Child**: Link parent to the child directly. - **Node with Two Children**: Replace the node with its in-order successor (smallest in the right subtree). **5. 2D Arrays (Array of Arrays)** A 2D array is an array of arrays, allowing for matrix-like structures: - **Creating**: int\[\]\[\] arr = new int\[rows\]\[cols\]; - **Accessing Elements**: Use arr\[row\]\[col\]. - **Iterating**: Nested loops are commonly used to access elements row by row. **6. ArrayList (Java ArrayList Class)** A resizable array-like structure: - **Adding Elements**: -.add(element): Adds to the end. -.add(index, element): Adds at a specific position. - **Removing Elements**: -.remove(index) or.remove(element): Removes by index or by element. - **Accessing Elements**:.get(index) retrieves an element at the specified position. - **Capacity Management**: Automatically resizes as needed. **Java-Specific Terms** - **Classes**: Blueprint for creating objects with defined attributes and behaviors. - **Extensions**: Use the extends keyword to create a subclass, inheriting properties and methods from the superclass. This overview provides a more in-depth explanation of each data structure\'s operations in Java, alongside core OOP principles and Java concepts like classes and extensions. Let me know if there\'s anything specific to expand on!