while-loops

While Loops Exercises

This directory contains exercises to help you practice writing while loops in Java using jshell.

Setup

1. Open your terminal/command prompt
2. Navigate to this directory
3. Start jshell: jshell
4. Load the exercise file: /open topic.jsh

Exercises

Exercise 1: Countdown

Write a method countdown(int start) that prints numbers from the start value down to 1, then prints "Blast off!".

Exercise 2: Sum Calculator

Write a method sumUpTo(int n) that calculates and returns the sum of all positive integers from 1 up to n (inclusive).

Exercise 3: Number Guessing Helper

Write a method findNumber(int target, int start) that starts from the start value and keeps adding 1 until it reaches the target. Return how many steps it took.

Exercise 4: Digit Counter

Write a method countDigits(int number) that counts and returns how many digits are in a positive integer. For example, 12345 has 5 digits.

Exercise 5: Password Strength Checker

Write a method checkPasswordStrength(String password) that returns:

• "Strong" if password has 8 or more characters
• "Medium" if password has 5-7 characters
• "Weak" if password has less than 5 characters

Use a while loop to count the characters in the password.

Exercise 6: Factorial Calculator

Write a method factorial(int n) that calculates n! (n factorial). For example, 5! = 5 × 4 × 3 × 2 × 1 = 120.

Exercise 7: Power Calculator

Write a method power(int base, int exponent) that calculates base raised to the power of exponent using a while loop (don't use Math.pow).

Testing Your Code

After completing each exercise, test your methods with different inputs:

// Example tests
countdown(5)        // Should print 5, 4, 3, 2, 1, Blast off!
sumUpTo(4)         // Should return 10 (1+2+3+4)
findNumber(10, 5)  // Should return 5 (5->6->7->8->9->10)
countDigits(12345) // Should return 5
factorial(5)       // Should return 120
power(2, 3)        // Should return 8 (2³)

Tips

• Read the NOTES.md file first to understand while loops
• Be careful with your loop conditions to avoid infinite loops
• Test with small values first, then try larger ones
• Make sure your loop variable changes inside the loop
• Consider edge cases like 0 or 1