What main methods and data structures ensure efficient information retrieval when using indexing mechanisms?

The following main methods and data structures are used for efficient information retrieval using index mechanisms:

• B-trees and B+-trees — balanced trees widely used in databases for indexing, providing logarithmic time for search, insert, and delete.
• Hash tables — provide quick access to data by key with amortized O(1) time, suitable for exact search.
• Inverted indexes — used in full-text search, where each word is associated with a list of documents or positions where it appears.
• Trie (prefix tree) — used for fast prefix searches, such as in autocomplete.

In Java, index structures are often implemented using collections from java.util, such as TreeMap (based on red-black trees) or HashMap. More complex indexes are implemented using specialized libraries and databases that support B-trees and inverted indexes.

Example of using TreeMap for indexing:

import java.util.TreeMap;

public class IndexExample {
    public static void main(String[] args) {
        TreeMap<String, Integer> index = new TreeMap<>();
        index.put("apple", 1);
        index.put("banana", 2);
        index.put("cherry", 3);

        // Search by key
        Integer value = index.get("banana");
        System.out.println("Index for banana: " + value);
    }
}