HashMap Data Structure Visualizer

How to Use

Initialize: Set map size (e.g., 8) and click "Initialize"
Sample Data: Click Sample Data to populate with examples.
Put: Enter key-value pair (e.g., Key: "user", Value: "Alice") and click "Put"
Get: Enter key (e.g., "user") to retrieve its value
Remove: Enter key (e.g., "user") to remove from map

HashMap Concept

HashMap is a key-value data structure that uses hashing for fast access and implements the Map interface.

Key Characteristics:

Stores key-value pairs with unique keys
Uses hash function for O(1) average access time
Handles collisions with separate chaining
Allows null values and one null key
Not synchronized (thread-unsafe)

Hash Calculation Example: For string "user" with map size 8:
Step 1: Calculate hashCode(): "user".hashCode() = 3599307
Step 2: Apply modulo: 3599307 % 8 = 3
Therefore, hash("user") = 3, so "user" is stored in bucket 3.

HashMap vs Hash Table

Key Differences:

Synchronization: HashMap is not synchronized (faster), Hash Table is synchronized (thread-safe)
Null Values: HashMap allows one null key and multiple null values, Hash Table doesn't allow nulls
Inheritance: HashMap extends AbstractMap, Hash Table extends Dictionary class
Performance: HashMap is faster due to no synchronization overhead
Iteration: HashMap uses fail-fast iterator, Hash Table uses enumerator (not fail-fast)

Applications

Caching and memoization
Database indexing
Configuration management
Counting and frequency analysis
Implementing sets and dictionaries

Time Complexity

Operation	Average	Worst
Put	O(1)	O(n)
Get	O(1)	O(n)
Remove	O(1)	O(n)

Space Complexity

Component	Space
Map Storage	O(n)
Load Factor	0.75

Strengths

Fast average-case operations
Flexible key-value mapping
Dynamic resizing
Memory efficient

Limitations

Not thread-safe
No ordering guarantee
Hash collision overhead
Memory overhead for small maps

HashMap Data Structure Visualizer

HashMap Setup

HashMap Operations

Hash Function

Statistics

HashMap Visualization

Operation Steps