Custom Calculator using exception

package com.company;
/*
        Question: You have to create a custom calculator with following operations:
        1. + -> Addition
        2. - -> Subtraction
        3. * -> Multiplication
        4. / -> Division
        which throws the following exceptions:
        1. Invalid input Exception ex: 8 & 9
        2. Cannot divide by 0 Exception
        3. Max Input Exception if any of the inputs is greater than 100000
        4. Max Multiplier Reached Exception - Don't allow any multiplication input to be greater than 7000
         */

class InvalidInputException extends Exception {
    public String toString() {
        return "Cannot add 8 and 9";
    }

    public String getMessage() {
        return "Getting Message";
    }
}
    class MaxInputException extends Exception {
        public String toString() {
            return "Number cannot be greater than 100000";
        }

        public String getMessage() {
            return "Getting Message";
        }
    }

    class CannotDivideByZeroException extends Exception {
        public String toString() {
            return "Cannot Divide By Zero";
        }

        public String getMassage() {
            return "Getting Message";
        }
    }

    class MaxMultiplyInputException extends Exception {
        public String toString() {
            return "Input Cannot be Greater than 7000";
        }

        public String getMassage() {
            return "Getting Message";
        }
    }

    class CustomCalculator {

        double add(double a, double b) throws InvalidInputException, MaxInputException, MaxMultiplyInputException {
            if (a > 100000 || b > 100000) {
                throw new MaxInputException();
            }

            if (a == 8 || b == 9) {
                throw new InvalidInputException();
            }
            return a + b;
        }

        double subst(double a, double b) throws MaxInputException {
            if (a > 100000 || b > 100000) {
                throw new MaxInputException();
            }

            return a - b;
        }

        double multiply(double a, double b) throws MaxInputException, MaxMultiplyInputException {
            if (a > 100000 || b > 100000) {
                throw new MaxInputException();
            } else if (a > 7000 || b > 7000) {
                throw new MaxMultiplyInputException();
            }
            return a * b;
        }
        double divide(double a, double b) throws CannotDivideByZeroException, MaxInputException {
            if (a > 100000 || b > 100000) {
                throw new MaxInputException();
            }
            if (b == 0) {
                throw new CannotDivideByZeroException();
            }
            return a / b;
        }
    }

    public class Main {

        public static void main(String[] args) throws InvalidInputException, CannotDivideByZeroException, MaxInputException, MaxMultiplyInputException {
 
            CustomCalculator cc = new CustomCalculator();
             cc.add(8,9);
            cc.divide(8, 0);
            cc.multiply(3,444444);
            cc.multiply(7000,7000);
        }
    }