Question

Modify the Triangle class (from previous code, will post under this) to throw an exception in the constructor and set routines if the triangle is not valid (i.e., does not satisfy the triangle inequality). Modify the main routine to prompt the user for the sides of the triangle and to catch the exception and re-prompt the user for valid triangle sides. In addition, for any valid triangle supply a method to compute and display the area of the triangle using Herod’s method: where a, b, and c are the lengths of the sides and p is 1/2 of the perimeter of the triangle, A = [p(p-a)(p-b)(p-c)]^1/2. The area, A, should be a double displayed with 2 digits after the decimal point. Supply a getPerimeter method to compute the perimeter as an integer. Display the triangle, its area and perimeter. Allow the user to repeatedly enter triangle sides and do not exit the process until the user enters 0 for a side length. Here is a sample dialog:

Enter the sides of the triangle as integers

Enter 0 to quit:

Enter side 1: 3

Enter side 2: 4

Enter side 3: 5

Triangle with sides: 3 4 5

Is right

Is not isosceles

Is not equilateral

Area = 6.00

Perimeter = 12

Enter the sides of the triangle as integers

Enter 0 to quit:

Enter side 1: 1

Enter side 2: 1

Enter side 3: 2

Not a valid triangle

Enter the sides of the triangle as integers

Enter 0 to quit:

Enter side 1: -1

Enter side 2: 2

Enter side 3: 3

Not a valid triangle

Enter the sides of the triangle as integers

Enter 0 to quit:

Enter side 1: 1

Enter side 2: 2

Enter side 3: 2

Is not right

Is isosceles

Is not equilateral

Area = 0.97

Perimeter = 5

Enter the sides of the triangle as integers

Enter 0 to quit:

Enter side 1: 0

Exiting

---------------------------------------------------------------------------

Program to modify:

TriangleDriver.java

package chegg1;
import java.util.Scanner;
public class TriangleDriver {

        public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                Triangle t;
                int x, y, z;
                System.out.println("Enter side A : ");
                x = in.nextInt();
                System.out.println("Enter side B : ");
                y = in.nextInt();
                System.out.println("Enter side C : ");
                z = in.nextInt();
                t = new Triangle(x, y, z);
                while(t.isInvalid()) {
                        System.out.println("Set side A: ");
                        t.setA(in.nextInt());
                        System.out.println("Set side B: ");
                        t.setB(in.nextInt());
                        System.out.println("Set side C: ");
                        t.setC(in.nextInt());
                }
                
                System.out.println(t.toString());
                System.out.println("Right angled: " + t.isRight());
                System.out.println("Equilateral: " + t.isEquilateral());
                System.out.println("Isosceles: " + t.isIsosceles());
        }

}

Triangle.java

package chegg1;

public class Triangle {
        private int a, b, c;
        boolean isValid;
        
        Triangle(int a, int b, int c){
                if(a+b<=c || b+c<=a || c+a<=b) {
                        this.isValid = false;
                }
                else {
                        this.isValid = true;
                        this.a = a;
                        this.b = b;
                        this.c = c;
                }
        }
        
        /**
         * @return the a
         */
        public int getA() {
                return a;
        }

        /**
         * @return the b
         */
        public int getB() {
                return b;
        }

        /**
         * @return the c
         */
        public int getC() {
                return c;
        }

        /**
         * @param a the a to set
         */
        public void setA(int a) {
                this.a = a;
                this.isValid = !this.isInvalid();
        }

        /**
         * @param b the b to set
         */
        public void setB(int b) {
                this.b = b;
                this.isValid = !this.isInvalid();
        }

        /**
         * @param c the c to set
         */
        public void setC(int c) {
                this.c = c;
                this.isValid = !this.isInvalid();
        }

        /* (non-Javadoc)
         * @see java.lang.Object#toString()
         */
        @Override
        public String toString() {
                return "Triangle [Side A =" + this.getA() + 
                                ", Side B =" + this.getB() + 
                                ", Side C =" + this.getC() + ", isValid =" + isValid + "]";
        }
        public boolean isInvalid() {
                if(this.a+this.b<=this.c ||this.b+this.c<=this.a ||this.c+this.a<=this.b)
                        return true;
                else
                        return false;
        }
        public boolean isRight() {
                boolean t = false;
                if(this.a<this.c && this.b<this.c) {                      //If c is the largest side
                        if(this.c*this.c == (this.a*this.a + this.b*this.b))
                                t = true;
                }
                else if(this.b<this.a && this.c<this.a) {         //if a is the largest side
                        if(this.a*this.a == (this.b*this.b + this.c*this.c))
                                t = true;
                }
                else{                                           //if b is the largest side
                        if(this.b*this.b == (this.a*this.a + this.c*this.c))
                                t = true;
                }
                return t;
        }
        public boolean isIsosceles() {
                if(this.a==this.b || this.a==this.c || this.b==this.c)
                        return true;
                else
                        return false;
        }
        public boolean isEquilateral() {
                if(this.a==this.b && this.a==this.c)
                        return true;
                else 
                        return false;
        }
}

---------------------------------------

Sorry for it being so long, please and thank you!!

Answer 1

import java.util.Scanner;

class Triangle {
        private int a, b, c;

        Triangle(int a, int b, int c) {
                if (isInvalid(a, b, c)) {
                        throw new IllegalArgumentException("invalid sides for triangle");
                }
                this.a = a;
                this.b = b;
                this.c = c;
        }

        /**
         * @return the a
         */
        public int getA() {
                return a;
        }

        /**
         * @return the b
         */
        public int getB() {
                return b;
        }

        /**
         * @return the c
         */
        public int getC() {
                return c;
        }

        /**
         * @param a the a to set
         */
        public void setA(int a) {
                if (isInvalid(a, b, c)) {
                        throw new IllegalArgumentException("invalid side for triangle");
                }
                this.a = a;
        }

        /**
         * @param b the b to set
         */
        public void setB(int b) {
                if (isInvalid(a, b, c)) {
                        throw new IllegalArgumentException("invalid side for triangle");
                }
                this.b = b;
        }

        /**
         * @param c the c to set
         */
        public void setC(int c) {
                if (isInvalid(a, b, c)) {
                        throw new IllegalArgumentException("invalid side for triangle");
                }
                this.c = c;
        }

        /*
         * (non-Javadoc)
         * 
         * @see java.lang.Object#toString()
         */
        @Override
        public String toString() {
                return String.format("Triangle [Side A =" + this.getA() + ", Side B =" + this.getB()
                + ", Side C =" + this.getC() + "]\n"
                + "Area: %.2f, Perimiter: %.2f", getArea(), getPerimeter()) ;
        }

        private boolean isInvalid(int a, int b, int c) {
                return (a + b <= c || b + c <= a || c + a <= b);
        }

        public boolean isRight() {
                boolean t = false;
                if (this.a < this.c && this.b < this.c) { // If c is the largest side
                        if (this.c * this.c == (this.a * this.a + this.b * this.b))
                                t = true;
                } else if (this.b < this.a && this.c < this.a) { // if a is the largest side
                        if (this.a * this.a == (this.b * this.b + this.c * this.c))
                                t = true;
                } else { // if b is the largest side
                        if (this.b * this.b == (this.a * this.a + this.c * this.c))
                                t = true;
                }
                return t;
        }

        public boolean isIsosceles() {
                if (this.a == this.b || this.a == this.c || this.b == this.c)
                        return true;
                else
                        return false;
        }

        public boolean isEquilateral() {
                if (this.a == this.b && this.a == this.c)
                        return true;
                else
                        return false;
        }
        
        public double getArea() {
                double s = (a + b + c) / 2.0;
                return Math.sqrt(s * (s - a) * (s - b) * (s - c));
        }
        
        public double getPerimeter() {
                return a + b + c;
        }
}
public class TriangleDriver {


        public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                
                Triangle t;
                int x, y, z;
                
                while(true) {
                        try {
                                System.out.println("Enter side A : ");
                                x = in.nextInt();
                                System.out.println("Enter side B : ");
                                y = in.nextInt();
                                System.out.println("Enter side C : ");
                                z = in.nextInt();
                                
                                if(x == 0 || y == 0 || z == 0) {
                                        break;
                                }

                                t = new Triangle(x, y, z);

                                System.out.println(t.toString());
                                System.out.println("Right angled: " + t.isRight());
                                System.out.println("Equilateral: " + t.isEquilateral());
                                System.out.println("Isosceles: " + t.isIsosceles());
                                System.out.println();
                        } catch(Exception e) {
                                System.out.println(e.getLocalizedMessage());
                                System.out.println();
                        }
                }
        }

}

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