Digital Gradebook (JavaBasics_Task_189_V0.1)

📖 Description

This project simulates a teacher's digital gradebook. It demonstrates how to use the containsKey() method in a HashMap to verify if a specific entry exists before attempting to retrieve and process its value. This approach prevents potential null pointer issues and ensures data integrity.

📋 Requirements Compliance

• Task: Create a HashMap<String, Integer> named studentGrades.
• Action: Add a record for "Anna" with a grade of 5.
• Validation: Check if the record for "Anna" exists using map properties.
• Output: Display Anna's grade only if the record is found.
• Goal: Master safe data retrieval techniques in associative arrays.

🚀 Architectural Stack

• Java 8+

🏗️ Implementation Details

The HashMap provides an efficient containsKey(Object key) method that returns a boolean. By using this method inside an if statement, we can safely access values. This is a fundamental pattern for handling dynamic data where certain keys might be missing.

📋 Expected result

Anna's grade: 5

💻 Code Example

Project Structure:

src/com/yurii/pavlenko/
                └── Solution.java

Code

package com.yurii.pavlenko;

import java.util.HashMap;
import java.util.Map;

public class Solution {

    public static void main(String[] args) {

        Map<String, Integer> studentGrades = new HashMap<>();
        studentGrades.put("Anna", 5);

        if (studentGrades.containsKey("Anna")) {
            Integer grade = studentGrades.get("Anna");
            System.out.println("Anna's grade: " + grade);
        } else {
            System.out.println("Record not found.");
        }
    }
}

⚖️ License

This project is licensed under the MIT License.

Copyright (c) 2026 Yurii Pavlenko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files...

License: MIT