Best practices in Java - Mini Project: Build & Apply

Best Practices in Java Programming

📖 Scenario: You are working on a small Java program to manage a list of books in a library. You want to write clean, readable, and maintainable code by following best practices.

🎯 Goal: Build a simple Java program that stores book titles and authors in a Map, uses a constant for the library name, iterates over the map with proper variable names, and prints the list of books clearly.

📋 What You'll Learn

Use meaningful variable names

Use constants for fixed values

Use proper indentation and spacing

Use enhanced for loop with descriptive variable names

Print output clearly with labels

💡 Why This Matters

🌍 Real World

Managing collections of data like books, products, or users is common in software. Writing clear and maintainable code helps teams work together and makes future changes easier.

💼 Career

Following best practices in Java is essential for professional developers to produce reliable, readable, and maintainable software that others can understand and improve.

1

Create the initial data structure

Create a Map<String, String> called books with these exact entries: "1984" : "George Orwell", "To Kill a Mockingbird" : "Harper Lee", and "The Great Gatsby" : "F. Scott Fitzgerald".

Java

# Create the Map called books with the given entries
// Your code here

Hint

Use Map<String, String> books = new HashMap<>(); and books.put(key, value); to add entries.

2

Add a constant for the library name

Add a final String constant called LIBRARY_NAME with the value "City Library" above the main method.

Java

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

public class Library {
    // Add the final String constant LIBRARY_NAME here
    
    public static void main(String[] args) {
        Map books = new HashMap();
        books.put("1984", "George Orwell");
        books.put("To Kill a Mockingbird", "Harper Lee");
        books.put("The Great Gatsby", "F. Scott Fitzgerald");
    }
    
    // Your code here
}

Hint

Use private static final String LIBRARY_NAME = "City Library"; before the main method.

3

Iterate over the books map with descriptive variable names

Use a for loop with variables title and author to iterate over books.entrySet() and print each book's title and author in the format: Title: [title], Author: [author].

Java

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

public class Library {
    private static final String LIBRARY_NAME = "City Library";

    public static void main(String[] args) {
        Map books = new HashMap();
        books.put("1984", "George Orwell");
        books.put("To Kill a Mockingbird", "Harper Lee");
        books.put("The Great Gatsby", "F. Scott Fitzgerald");

        // Use a for loop to iterate over books.entrySet() and print title and author
        // Your code here
    }
}

Hint

Use for (Map.Entry<String, String> entry : books.entrySet()) and get the key and value with entry.getKey() and entry.getValue().

4

Print the library name before the book list

Add a System.out.println statement to print the LIBRARY_NAME before the list of books.

Java

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

public class Library {
    private static final String LIBRARY_NAME = "City Library";

    public static void main(String[] args) {
        Map books = new HashMap();
        books.put("1984", "George Orwell");
        books.put("To Kill a Mockingbird", "Harper Lee");
        books.put("The Great Gatsby", "F. Scott Fitzgerald");

        // Print the library name here
        // Your code here

        for (Map.Entry entry : books.entrySet()) {
            String title = entry.getKey();
            String author = entry.getValue();
            System.out.println("Title: " + title + ", Author: " + author);
        }
    }
}

Hint

Use System.out.println("Library: " + LIBRARY_NAME); before the loop.

Practice

1. Which of the following is a best practice for naming variables in Java?

easy

A. Use clear and meaningful names like totalPrice instead of tp

B. Use single letters like x or y for all variables

C. Use all uppercase letters for variable names

D. Use names with special characters like total$price

Solution

1. Step 1: Understand variable naming clarity

   Clear and meaningful names help others understand the code easily.

2. Step 2: Compare options

   Use clear and meaningful names like totalPrice instead of tp uses descriptive names, while others use unclear or invalid styles.

3. Final Answer:

   Use clear and meaningful names like totalPrice instead of tp -> Option A

4. Quick Check:

   Meaningful variable names = Use clear and meaningful names like totalPrice instead of tp [OK]

Hint: Choose names that explain the variable's purpose [OK]

Common Mistakes:

• Using single letters for all variables
• Using uppercase for variable names (reserved for constants)
• Including special characters in names

2. Which of the following Java code snippets follows best practices for defining constants?

easy

A. int MAX_SIZE = 100;

B. final int maxSize = 100;

C. final int MAX_SIZE = 100;

D. int max_size = 100;

Solution

1. Step 1: Identify constant declaration rules

   Constants should be declared with final and use uppercase letters with underscores.

2. Step 2: Evaluate each option

   final int MAX_SIZE = 100; uses final and uppercase naming, matching best practices.

3. Final Answer:

   final int MAX_SIZE = 100; -> Option C

4. Quick Check:

   Constants use final + uppercase = final int MAX_SIZE = 100; [OK]

Hint: Constants use final and uppercase names [OK]

Common Mistakes:

• Not using final keyword for constants
• Using lowercase or camelCase for constant names
• Missing underscores in multi-word constants

3. What will be the output of the following Java code?

public class Test {
    public static void main(String[] args) {
        int x = 5;
        int y = 10;
        int sum = x + y;
        System.out.println("Sum is: " + sum);
    }
}

medium

A. Sum is: 510

B. Sum is: 15

C. Sum is: x + y

D. Compilation error

Solution

1. Step 1: Understand variable values and addition

   Variables x and y hold 5 and 10, sum is their addition: 5 + 10 = 15.

2. Step 2: Check output statement

   Prints "Sum is: " concatenated with sum value 15.

3. Final Answer:

   Sum is: 15 -> Option B

4. Quick Check:

   5 + 10 = 15 output = Sum is: 15 [OK]

Hint: Add numbers before printing to avoid string concatenation errors [OK]

Common Mistakes:

• Concatenating numbers as strings without addition
• Confusing variable names with strings
• Syntax errors from missing semicolons

4. Identify the best fix for the following Java code snippet that lacks proper indentation and comments:

public class Example {
public static void main(String[] args) {
int a=10;int b=20;int c=a+b;System.out.println(c);
}
}

medium

A. Add indentation and comments explaining variables

B. Remove all spaces to make code compact

C. Change variable names to single letters

D. Delete the print statement

Solution

1. Step 1: Recognize code readability issues

   Code is hard to read due to no indentation and no comments.

2. Step 2: Apply best practices

   Adding indentation and comments improves clarity and maintainability.

3. Final Answer:

   Add indentation and comments explaining variables -> Option A

4. Quick Check:

   Indentation + comments = Add indentation and comments explaining variables [OK]

Hint: Indent code blocks and add comments for clarity [OK]

Common Mistakes:

• Making code compact by removing spaces
• Using unclear variable names
• Removing useful print statements

5. You have a Java program that uses the number 3.14159 multiple times for calculations. What is the best practice to improve this code?

hard

A. Use a variable named piValue without final keyword

B. Keep using the number 3.14159 directly everywhere

C. Write the number as a string and convert it each time

D. Replace all occurrences with a constant named PI declared as final double PI = 3.14159;

Solution

1. Step 1: Identify magic number usage

   Repeated use of 3.14159 is a magic number and reduces clarity.

2. Step 2: Use a named constant

   Declaring final double PI = 3.14159; improves readability and maintainability.

3. Final Answer:

   Replace all occurrences with a constant named PI declared as final double PI = 3.14159; -> Option D

4. Quick Check:

   Use constants for magic numbers = Replace all occurrences with a constant named PI declared as final double PI = 3.14159; [OK]

Hint: Use final constants for repeated fixed values [OK]

Common Mistakes:

• Using magic numbers directly
• Using non-final variables for constants
• Converting numbers from strings repeatedly