2007 AP CSA FRQ 4: GameState
Topic: Inheritance & Game Simulation
Skills Tested: Subclass creation, polymorphism, game loop implementation, ArrayList with random
Curriculum Alignment: Unit 3 (Class Creation) (2025-2026 AP CSA)
Points: 9 | Time Estimate: ~22 minutes
Study This Topic: Unit 3: Class Creation Complete Study Guide
Part (a)
Write the complete RandomPlayer class that extends Player and selects moves randomly.
Try It First! Attempt to solve this part before viewing the solution.
Solution
public class RandomPlayer extends Player
{
public RandomPlayer(String name)
{
super(name);
}
public String getNextMove(GameState state)
{
ArrayList moves = state.getCurrentMoves();
if (moves.size() == 0)
return "no move";
int index = (int) (Math.random() * moves.size());
return moves.get(index);
}
} Part (b)
Write the play method that runs the game loop until completion, printing moves and announcing the winner.
Solution
public void play()
{
System.out.println(state);
while (!state.isGameOver())
{
Player player = state.getCurrentPlayer();
String move = player.getNextMove(state);
System.out.println(player.getName() + " " + move);
state.makeMove(move);
}
Player winner = state.getWinner();
if (winner != null)
System.out.println(winner.getName() + " wins");
else
System.out.println("Game ends in a draw");
}Key Concepts
✓ Use super(name) to call parent constructor
✓ Math.random() returns [0, 1), multiply by size for index
✓ Cast to int truncates to get valid array index
✓ Game loop continues while !isGameOver()
Common Mistakes to Avoid
✗ Forgetting to call super(name) in constructor
✗ Not handling empty moves list (size == 0)
✗ Incorrect random index calculation
✗ Not checking for null winner (draw case)
Official College Board Resources
About the Author: Tanner Crow is a certified AP Computer Science teacher with 11+ years of experience.
Last updated: January 2026