Java Set Interface Summary

Introduction to Java Set Interface

The Java Set Interface is a fundamental part of the Java Collections Framework, representing a collection that disallows duplicate elements.

Key Concepts

• Uniqueness: Sets automatically handle duplicates. If you try to add a duplicate element, it will not be added.
• Order: Sets do not guarantee any specific order of elements. However, some implementations, like LinkedHashSet, do maintain the insertion order.

Main Implementations

1. HashSet
   • Uses a hash table for storage.
   • No guaranteed order of elements.
   • Fast performance for basic operations (add, remove, contains).
2. LinkedHashSet
   • Maintains a linked list of the entries in the set, allowing for predictable iteration order (insertion order).
3. TreeSet
   • Implements the Set interface using a red-black tree.
   • Stores elements in a sorted order (natural ordering or custom comparator).

Example:

Set<Integer> treeSet = new TreeSet<>();
treeSet.add(5);
treeSet.add(1);
treeSet.add(3); // The set will be sorted: [1, 3, 5]

Example:

Set<String> linkedHashSet = new LinkedHashSet<>();
linkedHashSet.add("Apple");
linkedHashSet.add("Banana");
linkedHashSet.add("Cherry");

Example:

Set<String> hashSet = new HashSet<>();
hashSet.add("Apple");
hashSet.add("Banana");
hashSet.add("Apple"); // Duplicate, won't be added

Common Methods

• add(element): Adds the specified element to the set if it is not already present.
• remove(element): Removes the specified element from the set.
• contains(element): Checks if the set contains the specified element.
• size(): Returns the number of elements in the set.
• isEmpty(): Checks if the set is empty.

Example Usage

Here is a simple example demonstrating the usage of the HashSet:

import java.util.HashSet;

public class Main {
    public static void main(String[] args) {
        HashSet<String> fruits = new HashSet<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Apple"); // This will not be added

        System.out.println("Set of fruits: " + fruits); // Output: Set of fruits: [Banana, Apple]
    }
}

Conclusion

The Java Set Interface is crucial for handling collections of unique elements. Understanding the different implementations can help you choose the right type for your needs based on performance and order requirements.