Complete Guide to Data Structures in Java

Java offers several built-in data structures as part of its Java Collections Framework (JCF), as well as the ability to create custom structures.

1. Arrays

Arrays are one of the simplest data structures in Java. They store elements of the same data type in contiguous memory locations.

Characteristics of Arrays

• Fixed Size: The size of an array is defined at the time of creation.
• Index-Based Access: Each element is accessed using an index starting from 0.
• Homogeneous Data: All elements in an array are of the same type.

Example of Array in Java

Applications

• Storing collections of data.
• Performing matrix operations in mathematical computations.

2. Linked Lists

Linked Lists are dynamic data structures consisting of nodes, where each node contains data and a reference to the next node.

Types of Linked Lists

• Singly Linked List: Each node points to the next node.
• Doubly Linked List: Each node points to both the previous and next nodes.
• Circular Linked List: The last node points back to the first node.

Example of Linked List in Java

Applications

• Dynamic memory allocation.
• Implementing stacks and queues.

3. Stacks

Stacks follow the Last In, First Out (LIFO) principle. They are used for tasks requiring reverse ordering.

Operations

• Push: Add an element to the stack.
• Pop: Remove the top element.
• Peek: View the top element without removing it.

Example of Stack in Java

Applications

• Expression evaluation.
• Undo functionality in applications.

4. Queues

Queues operate on the First In, First Out (FIFO) principle. They are widely used in scenarios requiring sequential processing.

Types of Queues

• Simple Queue: Basic FIFO implementation.
• Priority Queue: Elements are processed based on priority.
• Deque: Double-ended queue allowing insertion and deletion at both ends.

Example of Queue in Java

Applications

• Task scheduling.
• Managing requests in servers.

5. Trees

Trees are hierarchical data structures with a root node and child nodes. They are used for representing hierarchical data.

Types of Trees

• Binary Tree: Each node has at most two children.
• Binary Search Tree (BST): A binary tree with ordered nodes.
• Heap: A complete binary tree for priority management.

Example of Tree in Java

Applications

• Database indexing.
• Directory structures in file systems.

6. Hash Tables

Hash Tables store data in key-value pairs, allowing constant-time complexity for insertions and lookups.

Example of Hash Table in Java

Applications

• Caching mechanisms.
• Implementing dictionaries.