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

Making the `x` field private prevents external classes from directly modifying its value, ensuring that any changes go through the `setX()` method which correctly calls `updateSum()` to maintain the invariant.

Making the `y` field private prevents external classes from directly modifying its value, ensuring that any changes go through the `setY()` method which correctly calls `updateSum()` to maintain the invariant.

Making the `sum` field private prevents external classes from directly modifying its value, ensuring that `sum` can only be updated internally by the `updateSum()` method, thereby maintaining the `x + y` invariant.

Making the constructor private would prevent the creation of `ComputeSum` objects, which is not the mechanism for protecting the internal `sum` invariant after object creation.

Making `setX()` private would prevent controlled modification of `x` from outside the class, forcing `x` to be immutable or requiring direct field exposure, which undermines the invariant protection.

Making `setY()` private would prevent controlled modification of `y` from outside the class, forcing `y` to be immutable or requiring direct field exposure, which undermines the invariant protection.