Java data validation question

[MBReikowsky]

Ok this is homework, and I have wrestled with this for quite awhile now. My program is supposed to give an error message if the user enters any invalid entries. The program works great when the user enters an invalid integer, but my problem is trying to get it to give an error message when the user enters an invalid entry when asked if they want to continue. Currently right now it just runs again if an invalid entry is entered. But I need it to give an error message if the user enters anything other than y or n. Id appreciate any help and suggestions on this. Thanks


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import java.util.*;
import java.text.*;
 
public class MReikowskyapp51
{
    public static void main(String[] args)
    {
        // welcome the user to the program
        System.out.println("Welcome to the Factorial Calculator");
        System.out.println();  // print a blank line
 
        // create a Scanner object named sc and intializ variables
 
 
        Scanner sc = new Scanner(System.in);
 
        // perform Factorial application when user enters "y" or "Y"
        String choice = "y";
        while (choice.equalsIgnoreCase("y"))
        {
            //get input from user
            int power = getIntWithinRange(sc,
            "Enter number greater than 0 and less than 10: ", 0, 10);
            long number = 1;
            //use a for loop to calculate the power
            for (int i = 1; i<= power; i++)
            {
 
                   number = number * i;
             }
                   System.out.println("power " + number + "\n");
                   String cont = "";
                   System.out.println("Continue? (y/n)");
                   cont = sc.next();
                   sc.nextLine();
                   System.out.println();
 
 
         }
}
public static int getInt (Scanner sc, String prompt)
{
    int i = 0;
    boolean isValid = false;
    while (isValid == false)
    {
        System.out.print(prompt);
        if (sc.hasNextInt())
        {
            i = sc.nextInt();
            isValid = true;
        }
        else
        {
            System.out.println
            ("Error! Invalid integer value. Try again.");
        }
        sc.nextLine(); //discard any other data entered on the line
    }
    return i;
}
    public static int getIntWithinRange (Scanner sc, String prompt, int min, int max)
    {
        int i = 0;
        boolean isValid = false;
        while (isValid == false)
        {
            i = getInt(sc, prompt);
            if (i <= min)
                System.out.println("Error! Number must be greater than " + min + ".");
 
            else if (i >= max)
            System.out.println("Error! Number must be less than " + max + ".");
 
            else
            isValid = true;
        }
        return i;
    }
  }//end program

[horace1]

the line

                   System.out.println("Continue? (y/n)");
                   cont = sc.next();
 

should be

                   System.out.println("Continue? (y/n)");
                   choice = sc.next();
 

because you test choice in

        while (choice.equalsIgnoreCase("y"))
        {
 

[MBReikowsky]

Ok thank you very much. My next question is where and how do I post the error message if something other than y or n is entered? Ive looked all over in my book and I couldnt find the command that will validate a string. I found plenty for numbers IE nextDouble but nothing that explains how to check the data they enter when they determine if they wish to continue or not?

[Ganon11]

You can use the .equals() function in the String class. No matter what they enter, you will be interpreting it as a String, whether it is actually a number, character, word, etc.

Once you have the input in a variable (choice?), use

choice.equals(" y");

to determine if it is y. You can use the same function to see if it is n. If it is neither y nor n (that is, !choice.equals( "y") && !choice.equals( "n")), then the user has entered a bad input.