1Z0-803 Question #223: Real Exam Question with Answer & Explanation

Given: public class ComputeSum { public int x; public int y; public int sum; public ComputeSum (int nx, int ny) { x = nx; y =ny; updateSum(); } public void setX(int nx) { x = nx; updateSum();} public void setY(int ny) { x = ny; updateSum();} void updateSum() { sum = x + y;} } This class needs to protect an invariant on the sum field. Which three members must have the private access modifier to ensure that this invariant is maintained?