Enhanced for loop in Java - Mini Project: Build & Apply

Enhanced for loop

📖 Scenario: You are organizing a small library system. You have a list of book titles that you want to display one by one to the user.

🎯 Goal: Learn how to use the enhanced for loop in Java to go through each item in a list and print it.

📋 What You'll Learn

Create a String array called books with exact titles

Create an integer variable count to count books

Use an enhanced for loop with variable book to iterate over books

Print each book title and the total count of books

💡 Why This Matters

🌍 Real World

Libraries, bookstores, or any system that manages lists of items can use enhanced for loops to process and display data easily.

💼 Career

Understanding enhanced for loops is essential for Java developers to write clean and readable code when working with collections or arrays.

1

Create the list of books

Create a String array called books with these exact titles: "Java Basics", "Data Structures", "Algorithms", "Design Patterns".

Java

# Create the String array books with the given titles

Hint

Use curly braces {} to list the book titles inside the array.

2

Add a counter variable

Add an integer variable called count and set it to 0 inside the main method, after the books array.

Java

public class Main {
    public static void main(String[] args) {
        String[] books = {"Java Basics", "Data Structures", "Algorithms", "Design Patterns"};
        // Create an int variable count and set it to 0
    }
}

Hint

Use int count = 0; to start counting from zero.

3

Use enhanced for loop to count books

Use an enhanced for loop with variable book to iterate over the books array. Inside the loop, increase count by 1.

Java

public class Main {
    public static void main(String[] args) {
        String[] books = {"Java Basics", "Data Structures", "Algorithms", "Design Patterns"};
        int count = 0;
        // Use enhanced for loop to iterate over books and increment count
    }
}

Hint

Use for (String book : books) to loop through each book.

4

Print each book and total count

Inside the enhanced for loop, add a System.out.println(book); statement to print each book title. After the loop, print the total number of books using System.out.println("Total books: " + count);.

Java

public class Main {
    public static void main(String[] args) {
        String[] books = {"Java Basics", "Data Structures", "Algorithms", "Design Patterns"};
        int count = 0;
        for (String book : books) {
            // Print the book title here
            count++;
        }
        // Print the total count here
    }
}

Hint

Use System.out.println(book); inside the loop and print the count after the loop.

Practice

1. What is the main purpose of the enhanced for loop in Java?

easy

A. To create infinite loops

B. To iterate over all elements in an array or collection easily

C. To declare variables with enhanced types

D. To replace if-else statements

Solution

1. Step 1: Understand the enhanced for loop usage

   The enhanced for loop is designed to simplify iterating over arrays or collections without manual index management.

2. Step 2: Compare options with the loop's purpose

   Only To iterate over all elements in an array or collection easily correctly describes this purpose; others describe unrelated concepts.

3. Final Answer:

   To iterate over all elements in an array or collection easily -> Option B

4. Quick Check:

   Enhanced for loop = easy iteration [OK]

Hint: Enhanced for loop = easy way to visit each item [OK]

Common Mistakes:

• Thinking it declares variables
• Confusing with infinite loops
• Using it to replace conditional statements

2. Which of the following is the correct syntax for an enhanced for loop iterating over an integer array nums?

easy

A. foreach (int num : nums) { System.out.println(num); }

B. for int num in nums { System.out.println(num); }

C. for (int num : nums) { System.out.println(num); }

D. for (num : nums) { System.out.println(num); }

Solution

1. Step 1: Recall Java enhanced for loop syntax

   The correct syntax uses: for (type variable : arrayOrCollection) { ... }

2. Step 2: Check each option

   for (int num : nums) { System.out.println(num); } matches the correct syntax. Options A, B, and C use incorrect keywords or missing parentheses.

3. Final Answer:

   for (int num : nums) { System.out.println(num); } -> Option C

4. Quick Check:

   Correct syntax uses ':' inside parentheses [OK]

Hint: Remember: for (type var : collection) { } [OK]

Common Mistakes:

• Using 'in' instead of ':'
• Omitting parentheses
• Using 'foreach' keyword in Java

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

int[] numbers = {1, 2, 3};
int sum = 0;
for (int n : numbers) {
    sum += n;
}
System.out.println(sum);

medium

A. 6

B. 123

C. 0

D. Compilation error

Solution

1. Step 1: Understand the loop operation

   The loop adds each element of the array (1, 2, 3) to the variable sum.

2. Step 2: Calculate the sum

   sum = 0 + 1 + 2 + 3 = 6

3. Final Answer:

   6 -> Option A

4. Quick Check:

   Sum of 1, 2, 3 = 6 [OK]

Hint: Sum all elements inside the loop [OK]

Common Mistakes:

• Concatenating numbers instead of adding
• Forgetting to initialize sum
• Syntax errors in loop

4. Identify the error in the following code snippet:

String[] fruits = {"apple", "banana", "cherry"};
for (String fruit : fruits) {
    System.out.println(fruits);
}

medium

A. Inside the loop, it should print 'fruit' instead of 'fruits'

B. The loop variable should be 'fruits' not 'fruit'

C. The array declaration is incorrect

D. Enhanced for loop cannot be used with arrays

Solution

1. Step 1: Analyze the loop variable and print statement

   The loop variable is 'fruit', representing each element. Printing 'fruits' prints the whole array reference each time.

2. Step 2: Correct the print statement

   To print each fruit, use 'System.out.println(fruit);' inside the loop.

3. Final Answer:

   Inside the loop, it should print 'fruit' instead of 'fruits' -> Option A

4. Quick Check:

   Print loop variable, not array name [OK]

Hint: Print the loop variable, not the array name [OK]

Common Mistakes:

• Printing the array variable inside the loop
• Confusing loop variable with array name
• Incorrect array declaration

5. Given a list of integers, which enhanced for loop code correctly counts how many numbers are greater than 10?

List<Integer> nums = List.of(5, 12, 7, 20, 10);
int count = 0;
// Which code correctly counts numbers > 10?

hard

A. for (Integer n : nums) { if (n >= 10) count++; }

B. for (int n : nums) { if (n >= 10) count++; }

C. for (n : nums) { if (n > 10) count++; }

D. for (int n : nums) { if (n > 10) count++; }

Solution

1. Step 1: Understand the data and requirement

   List.of(5,12,7,20,10). Numbers greater than 10: 12,20 (count=2).

2. Step 2: Recall enhanced for loop with List<Integer>

   Supports int n via automatic unboxing of Integer to int.

3. Step 3: Check each option

   A: >=10 counts 12,20,10 (3) incorrect.
   B: int n >10 correct syntax, condition, count=2.
   C: Missing type for n: compile error.
   D: >=10 incorrect condition.

4. Final Answer:

   for (int n : nums) { if (n > 10) count++; } -> Option D

5. Quick Check:

   int n works with List<Integer> via unboxing [OK]

Hint: int n works for List<Integer> via autounboxing [OK]

Common Mistakes:

• Using >= instead of >
• Missing type declaration for loop variable
• Wrong comparison operator