AP CSA 1.4 FRQ Practice: Locker Assignment

Unit 1: Using Objects and Methods · Lesson 1.4 · FRQ Practice

Locker Assignment

A free response question in the shape the exam uses: a stated contract, four rubric parts, and no main method handed to you. Worth 4 points.

Back to the Lesson 1.4 pageAll Unit 1 lessons

Why this question is worth four points

Assignment is not equality, and the order of assignments is the algorithm. This question walks a value through four reassignments and asks you to report it at each stage, which is the shape of every FRQ part that says "after the code segment executes".

What you are given

Two variables are declared and assigned for you: int locker and int shift.

The question

  1. (a) Print the starting locker number.
  2. (b) Move the locker forward by shift, then print it.
  3. (c) Double the locker number, then print it.
  4. (d) Move it back by shift, then print it.

What the reader is looking for

  1. Write a code segment that prints four lines in rubric order.
  2. Each part changes the SAME variable and then prints it. Do not print a fresh expression each time: the point of the question is that the value carries forward.
  3. Part (d) is the value after parts (b) and (c) have already happened, not the starting value minus shift.

Worked examples

These show what a correct answer prints. There are more cases you cannot see, and they use different values, so an answer built around just these numbers will fail.

Example 1 is given
int locker = 100;
int shift = 7;
Example 1 output
100
107
214
207
Example 2 is given
int locker = 15;
int shift = 35;
Example 2 output
15
50
100
65

Your answer

Main.java

Input for the Run button

How this is scored: your answer runs against every test case, and the fraction it passes becomes your score out of 4. That is not how a human AP reader marks a rubric, so treat the score as a check on whether your code works, and the rubric above as the thing you are actually practising.


  

  
Stuck?

    
Hint 1
locker = locker + shift reads right to left: work out the right side with the current value, then store the result back. It is not an equation and it is not a claim that the two sides are equal.

    
Hint 2
If your four printed lines can be worked out without knowing the previous one, you have written four independent expressions and the third and fourth will be wrong.

    
Hint 3
Part (d) subtracts from the DOUBLED value. (start + shift) * 2 - shift is not the same as start + shift * 2 - shift.



  
Where to go next

  

    Rework the Lesson 1.4 page
    Try the from-scratch exercise for this lesson
    Try the debugging exercise for this lesson
  


  
  






  

















  
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