Java If statement logic

Question

    System.out.println("Enter the answers pressing enter after every input : ");
    for(int x = 0; x < 20; x++) {
        do {
            studentAnswers[x] = keyboard.next().toUpperCase();
            System.out.println(studentAnswers[x]);
            if (!"A".equals(studentAnswers[x]) || !"B".equals(studentAnswers[x]) ||
                !"C".equals(studentAnswers[x]) || !"D".equals(studentAnswers[x]))
                System.out.println("You entered an invalid input.");
        } while(!"A".equals(studentAnswers[x]) || !"B".equals(studentAnswers[x]) ||
                !"C".equals(studentAnswers[x]) || !"D".equals(studentAnswers[x]));
    }

Above is my code. For whatever reason, the condition for both the if statement and do-while loop are not recognizing the correct inputs. For example, if I input a, it will print "You entered an invalid input." I even had my teacher look at this. Unfortunately, he could not find an answer either. The array studentAnswers is a String, and I even have the line below the input to ensure that the input is being stored correctly.

I would appreciate any help in solving this problem. Thanks in advance!

feco · Accepted Answer · 2016-10-26 21:17:36Z

5

You should replace || with && as you need all the conditions to be true to determine the input is invalid. With || only one condition is needed and it always will be true by your condition statement.

edited Oct 26, 2016 at 21:17

feco

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answered Oct 26, 2016 at 21:15

David Rojo

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7 Comments

baao Over a year ago

Worth to mention that "a".equals("A") is false

Red One Over a year ago

It worked! Thank you so much! I'm disappointed I didn't notice that after a good hour of staring at my code. However, there is one thing I'd like to point out. if(!"A".equals(studentAnswers[x]) When I was still in the troubleshooting stage, I changed my if statement to this only. It still wasn't working when I changed it to this alone. Why is that? There shouldn't have been an issue with logical operators.

Carcigenicate Over a year ago

@RedOne Impossible to say without knowing what the exact data used was. Could have been a mis-type for all we know.

blurb Over a year ago

@RedOne Why don't you try reproducing that bug for curiosity's sake?

Red One Over a year ago

drive.google.com/file/d/0BzlurahyqQgscjNjdDN2alhFRWM/… Here's a link. This is a version of the code right when I started.

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