Lab 02 10 pts Week 1 Due Apr 4

Lab 02: Character Stats

Declaring variables of every type and printing formatted output

variables types constants declarations
Clone from GitHub
3 checkpoints 5 autograder 2 timeliness
Prerequisites: lesson-1-2

After this lab, you will be able to:

  • Declare and initialize variables of type int, double, boolean, char, and String
  • Use final to declare constants that cannot be reassigned
  • Perform arithmetic that mixes int and double (requiring a cast)
  • Print variables with labels using string concatenation

What You’re Building

You will create a character stat sheet — like a tabletop RPG character card — that declares variables for every primitive type plus String, uses constants for fixed values, and computes a derived stat (HP percentage) that requires casting. The output is a formatted stat block printed to the console.

Concepts and Misconceptions

Concept Common Mistake What the Test Catches
Variable types Declaring double hp = 85 instead of 85.0 (works, but masks understanding) Type-specific tests verify declared types via source inspection
final constants Forgetting final, or naming constants in camelCase instead of UPPER_SNAKE Source scan for final keyword and naming convention
Casting int to double Writing currentHp / maxHp (integer division yields 0) Expected percentage is 0.0 instead of the correct value
String concatenation with numbers Expecting "HP: " + 85 + "/" + 100 to do math Prints correctly but students sometimes add parens in wrong places

Checkpoints

Checkpoint 1: Declare One of Each Type and Print

What to do: Declare at least one variable of each type: int, double, boolean, char, String. Print each on its own line with a label (e.g., "Level: 5").

What the test checks: Output contains one line per type with the correct label and value format.

Debugging tip: If the test expects "Active: true" and you print "Active: True", that is a failure. Java’s boolean prints as lowercase true/false. Do not capitalize.

Checkpoint 2: Use final Constants

What to do: Declare at least two final constants (e.g., MAX_HP, MAX_LEVEL) using UPPER_SNAKE_CASE. Use them in your output instead of raw numbers.

What the test checks: The source file contains final declarations. The test also verifies that reassigning a constant causes a compile error (this is structural — just make sure you used final).

Debugging tip: If you get “cannot assign a value to final variable,” that means final is working correctly. The error is telling you the constant is protected. Use a different variable if you need a mutable value.

Checkpoint 3: Compute HP Percentage with Casting

What to do: Given int currentHp and int maxHp, compute the HP percentage as a double. You must cast to avoid integer division: (double) currentHp / maxHp * 100.

What the test checks: The printed percentage matches the expected value (e.g., "HP: 85.0%"). Integer division would produce 0.0% or a wrong value.

Debugging tip: If your percentage prints 0.0, you are doing integer division. The cast must go on the numerator before the division: (double) currentHp / maxHp. Casting the result after division is too late — the truncation already happened.

How to Debug

  1. Check your types explicitly. If a test expects 85.0 and you print 85, the variable is an int when it should be a double. Add .0 to the literal or cast the expression.

  2. Print intermediate values. If the percentage is wrong, print currentHp, maxHp, and the raw division result on separate lines. This tells you exactly where the math goes wrong.

  3. Read the compiler error top-down. Java compiler errors point to the exact line and column. The first error is usually the real problem; errors after it are often cascading failures from the first.

Scoring

Component Points Criteria
Checkpoints 3 1 pt each. Binary: the checkpoint test passes or it does not.
Autograder 5 Correctness across all test cases. Partial credit by proportion of tests passed.
Timeliness 2 Full credit if submitted by the due date. 0 if late.
Total 10