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Java Java Basics Perfecting the Prototype Looping until the value passes

Daniel Makafui Ahiatrogah
Daniel Makafui Ahiatrogah
3,044 Points
Posted by Daniel Makafui Ahiatrogah
Daniel Makafui Ahiatrogah
3,044 Points

prompt user in a do while loop. the loop should continue while the response is No.

You are to declare a string variable. Prompt the user continually in a do while loop with the question "Do you understand do while loops? and store the result in string variable" The loop should continue to run while the response is No

Example.java 
// I have initialized a java.io.Console for you. It is in a variable named console

String response;

do {
  response = console.readLine("Do you understand do while loops?");
  if(response.equals(1))
     {
       System.exit(0);
     }

  }while(response.equals(0));
}

2 Answers

Steve Hunter
Steve Hunter
57,712 Points
Steve Hunter
Steve Hunter
57,712 Points

Hi Daniel,

I've copied your code and tweaked it a little:

String response;

do {
  response = console.readLine("Do you understand do while loops?");
 }while(response.equals("No"));

Make sense? The while does the testing, not an if.

Steve.

Rachelle Wood
Rachelle Wood
15,362 Points
Rachelle Wood
Rachelle Wood
15,362 Points

You can simplify your code (if you are on the second part of the challenge?).

Your variable declaration is correct, your prompt is correct, but your do while loop is the problem. Just have the do while loop keep prompting the prompt that you have there and set the condition in the while part to equal no.

String response;

do {
  response = console.readLine("Do you understand do while loops?");
} while (response == "No");
Steve Hunter
Steve Hunter
57,712 Points

While (no pun intended) testing for String equality with a double-equals can work, it is frowned upon as it can have some odd behaviours and produce inconsistent results. It's safest to use the String class' equals() or equalsIgnoreCase() methods for this. :-)

Rachelle Wood
Rachelle Wood
15,362 Points
Rachelle Wood
Rachelle Wood
15,362 Points

That is the first I am hearing that...

Rachelle Wood
Rachelle Wood
15,362 Points
Rachelle Wood
Rachelle Wood
15,362 Points

I checked up on this, and no it is not really frowned upon if you use it properly.

You are right that I did not use == properly in this case because what I did was to check for the equality between two objects. If you want to compare two string values then yes, .equals() is correct.

I guess I am getting Java confused with JavaScript where you can use === to check if the value of two strings is equal. In other languages I have played around with you can also use == or the equivalent to check for the value of two strings.

Steve Hunter
Steve Hunter
57,712 Points

It's frowned upon in the sense that it is unlikely to deliver the result you're expecting except in some rare circs with pooled strings or interned ones. The code looks absolutely fine but can chuck out some weird errors that are hard to pin down as the use of == can be so easily interpreted simply. I only mentioned it out of good practice - it is a point worth knowing, I think.

The SO community do a better job of explaining it than I do ... there's a useful link here