What are the ways to implement collection structures in Java?

In Java, there are several main ways to implement collection structures, which are represented in the java.util package:

• List — an ordered list of elements allowing duplicates.

  • ArrayList — implemented based on an array, provides quick access by index.
  • LinkedList — implemented as a doubly linked list, efficient for inserting and deleting elements.

• Set — a collection that does not allow duplicates.

  • HashSet — based on a hash table, does not guarantee the order of elements.
  • LinkedHashSet — preserves insertion order.
  • TreeSet — stores elements in sorted order.

• Map — stores key-value pairs.

  • HashMap — based on a hash table, does not guarantee order.
  • LinkedHashMap — preserves insertion order.
  • TreeMap — stores keys in sorted order.

There are also specialized collections, such as Stack, Queue, and Deque.

Example of using ArrayList:

import java.util.ArrayList;

ArrayList<String> list = new ArrayList<>();
list.add("Java");
list.add("Python");
System.out.println(list.get(0)); // Will output "Java"