Welcome to the introduction of hash tables in the Hash Tables tutorial! In this lesson, we will explore the concept of hash tables, a data structure that allows for efficient retrieval and storage of key-value pairs.

Hash tables provide fast access to data by using a technique called hashing. Hashing involves applying a hash function to a key to compute an index or address where the value is stored.

To understand hash tables, let's start with a basic analogy. Imagine you have a large library with thousands of books. Each book is assigned a unique identification number based on its title. When you want to find a specific book, you can quickly locate it by searching for its identification number.

Similarly, in a hash table, the keys are like book titles, and the hash function converts the keys into unique index values. This process allows for constant-time operations like insertion, retrieval, and deletion.

A hash table consists of two main components: an array and a hash function. The array is used to store the values, while the hash function maps the keys to their corresponding array indices.

Let's take a look at a simple example to understand this concept better:

1class Main {
2  public static void main(String[] args) {
3    // Create a hash table
4    HashTable<String, Integer> hashTable = new HashTable<>();
5
6    // Insert key-value pairs
7    hashTable.insert("Alice", 24);
8    hashTable.insert("Bob", 32);
9    hashTable.insert("Charlie", 41);
10
11    // Retrieve values
12    int age1 = hashTable.get("Alice");
13    int age2 = hashTable.get("Bob");
14    int age3 = hashTable.get("Charlie");
15
16    System.out.println("Alice's age: " + age1);
17    System.out.println("Bob's age: " + age2);
18    System.out.println("Charlie's age: " + age3);
19  }
20}