1. Introduction

A TreeMap is a part of the Java Collections Framework and extends the AbstractMap class. It is a Red-Black tree-based NavigableMap implementation, which means it maintains its keys in natural order or based on a provided comparator. In this guide, we’ll explore the CRUD (Create, Read, Update, Delete) operations on a TreeMap.

2. Program Steps

1. Initialize a TreeMap.

2. Populate the TreeMap with key-value pairs (Create).

3. Retrieve a value by its key from the TreeMap (Read).

4. Modify the value of an existing key (Update).

5. Remove a key-value pair from the TreeMap (Delete).

6. Display the final state of the TreeMap.

3. Code Program

import java.util.TreeMap;

public class TreeMapCRUDExample {
    public static void main(String[] args) {
        // 1. Initialize a TreeMap
        TreeMap<String, Integer> scores = new TreeMap<>();

        // 2. Populate the TreeMap with key-value pairs (Create)
        scores.put("Alice", 90);
        scores.put("Bob", 85);
        scores.put("Charlie", 88);
        System.out.println("Initial TreeMap: " + scores);

        // 3. Retrieve a value by its key from the TreeMap (Read)
        int aliceScore = scores.get("Alice");
        System.out.println("Score of Alice: " + aliceScore);

        // 4. Modify the value of an existing key (Update)
        scores.put("Alice", 92);
        System.out.println("Updated score of Alice: " + scores.get("Alice"));

        // 5. Remove a key-value pair from the TreeMap (Delete)
        scores.remove("Bob");
        System.out.println("After deleting Bob&apos;s score: " + scores);

        // 6. Display the final state of the TreeMap
        System.out.println("Final TreeMap: " + scores);
    }
}

Output:

Initial TreeMap: {Alice=90, Bob=85, Charlie=88}
Score of Alice: 90
Updated score of Alice: 92
After deleting Bob's score: {Alice=92, Charlie=88}
Final TreeMap: {Alice=92, Charlie=88}

4. Step By Step Explanation

1. A TreeMap is instantiated using its default constructor, ensuring that its entries are sorted according to their natural ordering.

2. The put method is employed to insert key-value pairs into the TreeMap.

3. By utilizing the get method, we can fetch the value linked with a particular key.

4. Updating the value of an existing key is done using the put method with a key that's already present.

5. The remove method lets us delete a given key-value pair from the TreeMap.

6. We print the state of the TreeMap several times during the program to monitor the various changes.

This tutorial provides a concise introduction to the basic CRUD operations using a TreeMap in Java, emphasizing its key sorting feature.