Creating a loop to check array (java)

Question

Homework assignment Suggestions only please as I wish very much to learn this as second nature! The goal is to create an array with a user specified question amount (array size) followed by an answer key (said array size now filled). Then to have the user input the "students" answers to check against key. I wrote all that no worries. Works lovely. The issue I am having is in two areas:

Create a loop that asks to grade another quiz.
Have it only check/score/calculate every other answer. ie: even answers only.

I have used a do/while loop to continue checking but couldn't get a sentinel value to stick. Also depending on where I placed it, the answers kept coming up as the first check. So I am unsure as to where to place and how to write it. I even tried to use a for loop boxing in the array and student answer portion to no avail. As regards to having it check every other one, I thought of modifying the count of "i" to something like ((i+1)*2) instead of i++ for the two for loops but I just get errors as that seems to not be proper at all.

Thank you in advance!

import java.util.Scanner;
import java.text.NumberFormat;

public class EvenQuizzes {
    public static void main(String[] args) {
        int quizQuest = 0, count = 0;
        double percentTotal = 0.0;
        Scanner scan = new Scanner(System.in);
        System.out.print("How many questions are in the quiz? Or enter 0 to quit. ");
        quizQuest = scan.nextInt();
        int[] answers = new int[quizQuest]; // scan in question total and apply
                                            // to array
        System.out.println("Enter the answer key: ");
        for (int i = 0; i < answers.length; i++) {
            answers[i] = scan.nextInt();
        }
        for (int i = 0; i < answers.length; i++) {
            System.out.println("Enter the answer to be graded : ");
            int toGrade = scan.nextInt();
            if (toGrade == answers[i]) {
                count++;
            }
        }
        percentTotal = ((double) count / quizQuest);
        NumberFormat defaultFormat = NumberFormat.getPercentInstance();
        defaultFormat.setMinimumFractionDigits(2);
        System.out.println("The questions answered correctly total: " + count);
        System.out.println("The percentage correct is: " + defaultFormat.format(percentTotal));
        System.out.println("\nAnother quiz to be graded?");
    }
}
// do ( quizQuest != 0){ //condition check to run new quiz against KEY
// for (int j = 0; (quizQuest = scan.nextInt()) != 0; j++); {

At the bottom is what I had considered for the loop portion I am having trouble with.

For checking whether it is even or not use,% and for continous loop until user terminates, search it either on google or stackoverflow, there are many similar questions — sam
– sam, Commented Oct 28, 2015 at 11:29
SO Community should pin this post as example for HOW TO ASK HOMEWORK QUESTIONS ON SO ;P — vish4071
– vish4071, Commented Oct 28, 2015 at 11:35
You can use modulo (%) to get the remainder after division (1 % 2 == 1). With this you can construct a loop with a branch that only does something whenever the condition matches. Alternatively, you can define your loop to increment by 2 each time around rather than 1. It will be worth reading up on both approaches and using the one you think fits best. — SlopeOak
– SlopeOak, Commented Oct 28, 2015 at 11:37

vish4071 · Accepted Answer · 2015-10-28 11:33:10Z

1

As you asked for hints (and not the code), here it is:

For more than one quizzes, use do-while, as follows:

do{
    //do something
    //scan the value of quiz quest
    //do something
}while(quizquest != 0)

Now, if only answers at even positions are to be checked, do following:

for (int i =0; i <answers.length; i++)
   {

       System.out.println("Enter the answer to be graded : ");
       int  toGrade = scan.nextInt();

       if(i % 2 == 0 && toGrade == answers[i]){   
          count++ ;

       }


   }

answered Oct 28, 2015 at 11:33

vish4071

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2 Comments

GoldenDesign Over a year ago

Thank you! It got the wheels turning! I'll have this spit out in no time now.

vish4071 Over a year ago

Glad it helped. Accept the answer by clicking the green tick :)

user5482783 · Accepted Answer · 2015-10-28 11:33:22Z

1

Create a loop that asks to grade another quiz: You could use a do-while loop with a boolean indicating if the user (teacher?) wants to grade another quiz:

do{
    boolean continue = false; 
    // check if the user wants to continue
while(continue);

Have it only check/score/calculate every other answer. ie: even answers only: You can check for even answers with the modulo operator:

if(i % 2 == 0){
    // even answer
}

Hope this helps!

answered Oct 28, 2015 at 11:33

user5482783

1 Comment

GoldenDesign Over a year ago

Thank you! I hadn't considered the modulo operator. I had a do/while placed within before but ran into errors with it only keeping the first grade. So when I tested it with 4 questions half right then did all right both outputs showed a score of 50%. I need to play with placement of the do{

ragingasiancoder · Accepted Answer · 2016-06-30 17:40:42Z

0

You should have a variable, perhaps named continue, whose default value is 'Y'. At the very beginning, create a while loop that checks the condition continue==Y, and at the end when you ask "Another quiz to be graded?", read in the input to the variable continue.

edited Jun 30, 2016 at 17:40

ragingasiancoder

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answered Oct 28, 2015 at 11:32

Shivam

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