Can you explain how the Set data structure works and how it stores unique values?

The Set data structure in Java represents a collection that stores unique elements without a specific order. The main mechanism to ensure uniqueness is the use of the equals() method for comparing objects and hashCode() for quick lookup.

For example, HashSet implements Set based on a hash table. When adding an element, its hash code is computed, which determines its position in the table. If there is already an element with the same hash code at that position, equals() is called to check for equality. If the element is already present, the addition does not occur, ensuring uniqueness.

Example of using HashSet:

import java.util.HashSet;

HashSet<String> set = new HashSet<>();
set.add("apple");
set.add("banana");
set.add("apple"); // will not be added, as "apple" already exists

System.out.println(set); // Will output [banana, apple]

Thus, Set ensures the storage of unique values through hashing and equality checks.