Multiple choice quiz source code JAVA

Question

I have implemented the following code. I just want the program to keep prompting the user until a valid response is entered. Can anyone help? I want that if user enters any other character other than A, B , C or D, the program ask the user to input valid option.

import java.io.*;

import java.util.*;

import java.util.Scanner;

public class Main {

static Scanner cin = new Scanner(System.in);

public static void main(String[] args){

int correct = 0;

int incorrect=0;

int questions = 5;

System.out.println("Welcome to the Multiple Choice Quiz! \n");

String[][] Ques_Ans = {

{"What is the size of float variable? ","\n A. 8 bit \n B. 16 bit \n C. 32 bit \n D. 64\n","C"},

{"Which one of these is not a primitive data type? ","\n A. integer \n B. char \n C. float \n D. double\n","B"},

{"Which data type is used to create a variable that should store text? ","\n A. myString \n B. string \n C. character \n D. String64\n","D"},

{"How do you create a variable with the numeric value 5? ","\n A. num x = 5; \n B. float x = 5; \n C. x = 5; \n D. int x = 5;\n","A"},

{"Which method can be used to find the length of a string in JAVA?","\n A. length() \n B. getlength() \n C. len \n D. getsize()\n","A"}};

String[] user_ans = new String[(int) questions];

int i=0;

do {

System.out.print("" + (i+1) + ". " + Ques_Ans[i][0] + " "+Ques_Ans[i][1]);

user_ans[i] = String.valueOf(cin.next().charAt(0));

isValid(user_ans);

if(Ques_Ans[i][2].equals(user_ans[i])) {

System.out.println("\n Correct!");

correct++;

}

else

{

System.out.println("\n Incorrect. The correct answer is "+Ques_Ans[i][2]);

incorrect++;

}

System.out.print("\n");

i++;

}while(i<questions));

System.out.println("\n Number of correct answers: "+ correct);

System.out.println("\n Number of incorrect answers: "+ incorrect);

System.exit(0);

}

}

Answer 1

A simple way you can achieve this would be to have a while-loop inside the main loop of your quiz code which checks your input variable value.

You would set the initial value of the variable that holds the value of the users input to a default string and check to make sure that you keep asking the user for an input while the value of that input is not equal to your desired inputs of: ['D', 'C', 'B', 'A']

You can achieve this using the logical '&&' (and) operator to check and make sure that if the input is not equal to any of the acceptable input you continue looping for an input. This way each time the user inputs a value, the program does not move on until it sees a recognized input.

Specifically in pseudo-code you would write this:

do {

user_ans[i] = "";

do {

user_ans[i] = USER_INPUT

} while(user_ans[i] != 'D' && user_ans[i] != 'C' && user_ans[i] != 'B' && user_ans[i] != 'A');

continue_main_loop_logic();

} while ()

Answer 2

char ch;

Console console= System.console();

Stting inbuff;

do

{

System.out.print(" Please input your response :>"):

inbuff= console.readLine();

ch=inbuff.charAt(0);

}

while (

(ch!='A') && (ch!='B') &&(ch!='C') &&(ch!='D')

);