Question

First, design and implement a class Triangle, which includes the attributes -- sideA, sideB, and sideC; behaviors: regular constructor, mutators, assessors, and area(). Second, design user-defined Exception to handle the following two execution error: negative edge value the sum of two sides' length is small than that of the third side.

In Java and Test please

Answer 1

class Triangle {

    public static class InvalidTriangleException extends Exception {
        public InvalidTriangleException() {
        }

        public InvalidTriangleException(String message) {
            super(message);
        }
    }

    private double sideA, sideB, sideC;

    public Triangle() {
    }

    public Triangle(double sideA, double sideB, double sideC) throws InvalidTriangleException {
        setSideA(sideA);
        setSideB(sideB);
        setSideC(sideC);
    }

    public double getSideA() {
        return sideA;
    }

    public void setSideA(double sideA) {
        this.sideA = sideA;
    }

    public double getSideB() {
        return sideB;
    }

    public void setSideB(double sideB) {
        this.sideB = sideB;
    }

    public double getSideC() {
        return sideC;
    }

    public void setSideC(double sideC) {
        this.sideC = sideC;
    }

    private void validateSide(double side) throws InvalidTriangleException {
        if (side < 0) {
            throw new InvalidTriangleException("error: negative edge value");
        } else if ((sideA >= sideB + sideC) || (sideB >= sideA + sideC) || (sideC >= sideA + sideB)) {
            throw new InvalidTriangleException("error: the sum of two sides' length is small than that of the third side");
        }
    }

    public double area() throws InvalidTriangleException {
        validateSide(sideA);
        validateSide(sideB);
        validateSide(sideC);
        double p = (sideA + sideB + sideC) / 2;
        return Math.sqrt(p * (p - sideA) * (p - sideB) * (p - sideC));
    }
}

class TestTriangle {

    public static void main(String[] args) {
        try {
            Triangle t1 = new Triangle();
            t1.setSideA(3);
            t1.setSideB(4);
            t1.setSideC(5);
            System.out.println("Area is " + t1.area());
        } catch (Triangle.InvalidTriangleException e) {
            System.out.println(e.getMessage());
        }

        try {
            Triangle t1 = new Triangle();
            t1.setSideA(3);
            t1.setSideB(4);
            t1.setSideC(10);
            System.out.println("Area is " + t1.area());
        } catch (Triangle.InvalidTriangleException e) {
            System.out.println(e.getMessage());
        }
    }
}