Question

Could someone re-write this code so that it first prompts the user to choose an option from the calculator (and catches if they enter a string), then prompts user to enter the values, and then shows the answer. Also, could the method for the division be rewritten to catch if the denominator is zero. I have the bulk of the code. I am just having trouble rearranging things.

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import java.util.*;

abstract class CalculatorNumVals
{
int num1,num2;

CalculatorNumVals(int value1,int value2)
{
num1=value1;
num2=value2;
}

public String toString()
{
return "Numbers are "+num1+"\t"+num2+"\n";
}

abstract void add();
abstract void subtract();
abstract void multiply();
abstract void division();
}

class CalFunctions extends CalculatorNumVals
{
CalFunctions(int value1,int value2)
{
super(value1,value2);
}

void add()
{
int ans;
ans=num1+num2;
System.out.println("Addition of two numbers is "+ans);
System.out.println();
}

void subtract()
{
int ans;
ans=num1-num2;
System.out.println("Subtraction of two numbers is "+ans);
System.out.println();
}

void multiply()
{
int ans;
ans=num1*num2;
System.out.println("Multiplication of two numbers is "+ans);
System.out.println();
}

void division()
{
double ans;
ans=(double)num1/num2;
System.out.println("Division of two numbers is "+ans);
System.out.println();
}
}
class CalculatorDemo
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
int val1,val2,choice;

System.out.print("\nEnter number 1 : ");
val1=sc.nextInt();
System.out.print("Enter number 2 : ");
val2=sc.nextInt();
System.out.println("\nOperations of Calculator :");
System.out.println("-----------------------------------------------------------------");
System.out.println("\n1. Addition\n2. Subtraction\n3. Multiplication\n4. Division\n");
System.out.println("-----------------------------------------------------------------\n");
CalFunctions cal=new CalFunctions(val1,val2);
System.out.println(cal);

System.out.print("Enter your choice : ");
choice=sc.nextInt();

System.out.println();

switch(choice)
{
case 1:cal.add();
break;
case 2:cal.subtract();
break;
case 3:cal.multiply();
break;
case 4:cal.division();
break;
default:System.out.println("Invalid case\n");
break;
}
}
}

Answer 1

import java.util.*;

abstract class CalculatorNumVals {

int num1, num2;

CalculatorNumVals(int value1, int value2) {

num1 = value1;

num2 = value2;

}

public String toString() {

return "Numbers are " + num1 + "\t" + num2 + "\n";

}

abstract void add();

abstract void subtract();

abstract void multiply();

abstract void division();

}

class CalFunctions extends CalculatorNumVals {

CalFunctions(int value1, int value2) {

super(value1, value2);

}

void add() {

int ans;

ans = num1 + num2;

System.out.println("Addition of two numbers is " + ans);

System.out.println();

}

void subtract() {

int ans;

ans = num1 - num2;

System.out.println("Subtraction of two numbers is " + ans);

System.out.println();

}

void multiply() {

int ans;

ans = num1 * num2;

System.out.println("Multiplication of two numbers is " + ans);

System.out.println();

}

void division() {

double ans = 0;

try {

ans = (double) num1 / num2;

} catch (Exception e) {

System.out.println(e.getMessage());

}

System.out.println("Division of two numbers is " + ans);

System.out.println();

}

}

class CalculatorDemo {

public static void main(String args[]) {

Scanner sc = new Scanner(System.in);

int val1, val2, choice = 0;

while (choice != -1) {

System.out.println("\nOperations of Calculator :");

System.out.println("-----------------------------------------------------------------");

System.out.println("\n1. Addition\n2. Subtraction\n3. Multiplication\n4. Division\n 5 Exit");

System.out.println("-----------------------------------------------------------------\n");

System.out.print("Enter your choice : ");

choice = sc.nextInt();

if (choice == -1)

break;

System.out.print("\nEnter number 1 : ");

val1 = sc.nextInt();

System.out.print("Enter number 2 : ");

val2 = sc.nextInt();

System.out.println();

CalFunctions cal = new CalFunctions(val1, val2);

System.out.println(cal);

switch (choice) {

case 1:

cal.add();

break;

case 2:

cal.subtract();

break;

case 3:

cal.multiply();

break;

case 4:

cal.division();

break;

case 5:

choice = -1;

break;

default:

System.out.println("Invalid case\n");

break;

}

}

}

}

$Console X CalculatorDemo [Java Application] C:\Program FilesJavare1.8.0_144\binjavaw.exe (Nov 22, 2018, 9:42:13 AM) Enter your choice: 1 Enter number 1 10 Enter number 2 20 Numbers are 10 20 Addition of two numbers is 30 Operations of Calculator: 1. Addition 2. Subtraction 3. Multiplication 4. Division 5 Exit Enter your choice: 1 Enter number 1 10 Enter number 2 12 Numbers are 10 Addition of two numbers is 2 12 Operations of Calculator: 1. Addition 2. Subtraction 3. Multiplication 4. Division 5 Exit Enter your choice:$