Part (a)

Write the complete APLine class representing a line ax + by + c = 0.

Solution

public class APLine
{
    private int a, b, c;
    
    public APLine(int a, int b, int c)
    {
        this.a = a;
        this.b = b;
        this.c = c;
    }
    
    public double getSlope()
    {
        return -a / (double) b;
    }
    
    public boolean isOnLine(int x, int y)
    {
        return a * x + b * y + c == 0;
    }
}

Part (b)

Note: This was a single-part question requiring the complete class.

Solution

// Key insight: DO NOT store slope as instance variable
// Calculate it from a and b when needed
// Cast to double to avoid integer division

Key Concepts

Common Mistakes