help with Scanner

[bvav22]

Hey guys, im trying to finish an assignment for a java class, and i have finished the program except for one part. The program requires that i take 3 values inputted from the user, the first 2 must be digits between 0 and 9, and the third an operator.
the operator decides if the two numbers are added subtracted...et c. anyways the things i cannot get, is i need to check if they enter valid digits, and not letters, however if i do put a letter in, scanner gives me an exception. it happens at line 14 when you enter a letter.... how can i test if it is a letter... any suggestions?


here is my code

import java.util.Scanner;
import java.text.DecimalFormat;

public class problem1 {
public static void main(String[]args){
	
	double num1,  num2, answ;

	String tString,num1Word = " ",num2Word= " ";
	Scanner scan = new Scanner(System.in);
	DecimalFormat formatter = new DecimalFormat("0");
	
	System.out.println("Please enter two numbers between 0 and 9 ");
	num1= scan.nextDouble();
	num2= scan.nextDouble();
	
	if(Character.isDigit((Double.toString(num1)).charAt(0))){
		
	}
	else{System.out.println("Please Enter Digits only!");
	System.exit(0);
	}
	
	switch((int)num1){
	case 0: num1Word= "Zero";
	break;
	case 1: num1Word= "One";
	break;
	case 2: num1Word= "Two";
	break;
	case 3: num1Word= "Three";
	break;
	case 4: num1Word= "Four";
	break;
	case 5: num1Word= "Five";
	break;
	case 6: num1Word= "Six";
	break;
	case 7: num1Word= "Seven";
	break;
	case 8: num1Word= "Eight";
	break;
	case 9: num1Word= "Nine";
	break;
	default: 
		System.out.println("Invalid Number");
	System.exit(0);
	break;
	}
	switch((int)num2){
	case 0: num2Word= "Zero";
	break;
	case 1: num2Word= "One";
	break;
	case 2: num2Word= "Two";
	break;
	case 3: num2Word= "Three";
	break;
	case 4: num2Word= "Four";
	break;
	case 5: num2Word= "Five";
	break;
	case 6: num2Word= "Six";
	break;
	case 7: num2Word= "Seven";
	break;
	case 8: num2Word= "Eight";
	break;
	case 9: num2Word= "Nine";
	break;
	default: 
		System.out.println("Invalid Number");
	System.exit(0);
	break;
	}
	System.out.println("Please enter the mathematical symbol for what you would like to do with these numbers. ");
	tString = scan.next();
	char operator = tString.charAt(0);
	
	

	
	switch(operator){
	case '*': answ= num1*num2;
		System.out.println(num1Word+ " Multiplied by "+num2Word+" is "+formatter.format(answ));
		break;
	case '/': if(num2 == 0){
		System.out.println("You cannot divide by zero, session terminated.");
		
	}
	else{
		answ= num1/num2;
		System.out.println(num1Word+ " Divided by "+num2Word+" is "+formatter.format(answ));
	}
	break;
	case '+': answ= num1 + num2;
	System.out.println(num1Word+ " Added to "+num2Word+" is "+formatter.format(answ));
	break;
	case '-': answ= num1 - num2;
	System.out.println(num1Word+ " Minus "+num2Word+" is "+formatter.format(answ));
	break;
	case '^': 
		answ= Math.pow(num1,num2);
	System.out.println(num1Word+ " raised to the power of " +num2Word+ " is "+ formatter.format(answ));
	break;
	default: System.out.println("Invalid Operator");
	System.exit(0);
	break;
	}

}
}

[horace1]

you can use method scanner.hasNext Double() to check if the next token can be read as a double and if not ignore it, e.g.

System.out.println("Please enter two numbers between 0 and 9 ");
while(!scan.hasNextDouble())
   { 
    System.out.printf("error, enter a double !"); 
    scan.nextLine();          // ignore rest of line
   }
num1= scan.nextDouble();

[bvav22]

i really cannot thank you enough, that was such a big help.... :)