Out of Subset Responses and the 2025 Free Response Questions

The APCSA exam for 2025 was administered on May 7th. The free response questions were released to AP Central and can be found here.

All of these questions can be solved within the AP Java subset; however, there are other ways to solve these problems that are outside of the Java subset. Some of these solutions use newer Java features, such as records and the use of methods in the SequencedCollection class. In this article, we will showcase solutions that use out of subset content.

Free Response Question 1: Dog Walker

Part A - In this solution, we will use var and the ternary conditional operator, both of which are outside the AP Java Subset.

public int walkDogs(int hour) {
    var numDogAvail = company.numAvailableDogs(hour);
    var dogsWalked = (numDogAvail >= maxDogs) ? maxDogs : numDogAvail;
    company.updateDogs(hour, dogsWalked);
    return dogsWalked;
}

While this solution is acceptable, the use of var with numDogAvail is not recommended as it is less readable when used to hold the return value of a method. We are not sure what the return type of numAvailableDogs is without also referencing this method. In this case, we can guess that the value returned is an int, but again, it isn't intuitive.

Rather than using an if statement to check and see if the numDogAvail is greater than maxDogs, we can use a ternary conditional operator and assign dogsWalked to the appropriate value based on this condition.

Part B - In this solution, we will also be using var and the ternary conditional operator.

public int dogWalkShift (int startHour, int endHour) {
    var amountEarned = 0;
    for (var h = startHour; h <= endHour; h++) {
        var numDogs = walkDogs(h);
        amountEarned += ((h >= 9 && h <= 17) || numDogs == maxDogs)
                        ? numDogs * 5 + 3 : numDogs * 5;
    }
}

In this case, amountEarned and h are excellent candidate for the use of var. The numDogs variable can use var, but again since it is holding the value from a method it isn't the best use of var.

The if statement to determine amountEarned can also be replaced by a ternary conditional operator.

Free Response Question 2: SignedText

The SignedText class can be written as a record, which is a type of class. It is an excellent candidate for a record, since the first name and last name are not expected to change when using this class. Using a record in this case means that the instance variables and constructor for the class are created automatically. Students still need to write all the logic for the getSignature and addSignature methods.

public record SignedText(String firstName, String lastName) {
   public String getSignature() {
      return (firstName.length() == 0) ? lastName 
                             : firstName.substring(0, 1) + "-" + lastName;
   }

    public String addSignature (String memo) {
       var signature = getSignature();
       var index = memo.indexOf(signature);
       return (index == -1) ? memo + signature  
                        : ((index == 0) 
                        ? (memo.substring(signature.length()) + signature) 
                        : memo);
    }
}

This solution also made use of var and the ternary conditional operator.

In the method getSignature, the ternary conditional operator can be used to create the signature under the condition of whether or not firstName is an empty string or not.

In the method addSignature, var is being used for the return values for a call to getSignature and indexOf method. These are both cases where var can be used. The method getSignature is within this class, so it isn't too difficult to figure out the return type and indexOf is a common method for String. But these are still less intuitive cases and for readability sake, not the best candidates for var.

In addSignature, we are also using the ternary conditional operator. This time it is nested. There is the check for whether signature is in memo and, if it is, a check to see if signature appears at the beginning of the memo.

Free Response Question 3: Competition

Part A - You can certainly use var in this solution.

Part B - In this solution, you will see var, ternary conditional operator and the use of methods from SequencedCollection class.

public ArrayList<Match> buildMatches(){
    var copy = new ArrayList<Compet>();
    var retMatches = new ArrayList<Match>();
 
    for (var c: competitorList){
        copy.add(c);
    }
 
    var first = (copy.size() % 2 == 1) ? copy.removeFirst() 
                                       : copy.getFirst();
    while (copy.size() != 0) {
        var match = new Match (copy.removeFirst(), copy.removeLast());
        retMatches.add(match);
    }
    return retMatches;
}

The uses of var for copy, retMatches, c, and match are all really good choices. Using it for first is less intuitive since it is the return value of a method.

To use the remove methods of the SequencedCollection class, we need to make a copy of the ArrayList so we don't destroy the original set of data. Once this is complete, we can remove the first element if the ArrayList has an odd number of elements. And then match up the first and last elements using a while loop and removing the ones that have been matched from the list with the removeFirst and removeLast methods.

This solution also uses the ternary conditional operator to remove the first element. However, since there was no change to the ArrayList if the length was already even, we had to do something arbitrary that also didn't impact the solution. That is why we used getFirst in that case. An if statement would have been cleaner in this case.

Free Response Question #4: SumorSamePuzzle

This FRQ can leverage var in the solutions similar to the questions above.

Disclaimer

It is not recommended for students to write solutions that are outside the AP Java Subset as the questions are written with the subset in mind. Students should be wary of writing the solutions above on the exam, since readers are trained on in subset solutions. Readers do their very best to not penalize students for correct solutions, but if a reader doesn't recognize the code because it is unexpected, it could be scored incorrectly.

Hoping all your students scored a 5!