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Thread: Newbie Needs Help

  1. #1
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    Default Newbie Needs Help

    Hi guys, I entered into a computer science course and I might need this forum for any upcoming projects. With that being said, so far, I learned up from putting integers, doubles, strings, bufferedreader, output to user (the System.out.println), input from user to program (for example num1= Integer.parseInt(myInput.readLine()); ), basic operations of math(adding,subtracting etc.), Math.floor/ceil, for loops, do...while loops, changing words into number of letters being a number, specific decimal places, while loops, if and if else statements.
    Now, my teacher just taught us how to do switch and case.
    and I'm having a problem involving loops.
    The program that we are doing right now involves us looping something if the user does not input anything.
    For example:

    switch (num1)
    {case 1:
    System.out.println ("You have selected Mathematics");
    do
    {System.out.println ("Please enter your average for mathematics.");
    num2= Integer.parseInt(myInput.readLine());}
    while (num2==blank);
    //where String blank= "";

    Can anybody help me on this? I do not know how to do any Boolean even though it is requested in the program when I get the error. Thanks in advance


  2. #2
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    Default Re: Newbie Needs Help

    Quote Originally Posted by DJMS View Post
    ...so far, I learned up from putting integers, doubles, strings, bufferedreader, output to user (the System.out.println), input from user to program yaada, yaada, yaada...
    OK. You have learned a lot. We get it.


    Quote Originally Posted by DJMS View Post
    The program that we are doing right now involves us looping something if the user does not input anything.
    Now, you have to define "anything."

    I mean, if the program is executing some kind of readLine() function from the System.in stream, and I, the user, don't do "anything," it waits for me to do "something." Now, in this case "something" is defined as pressing zero or more character keys in sequence. The sequence is terminated when I, the user, press the 'Enter' key. Until I, the user, press 'Enter' nothing is presented to the program, even though it can't really be said that I am "not doing anything." I mean, I'm pushing keys like crazy. I just haven't hit 'Enter' yet.


    Now as for your bit of code:

    Assuming myInput is a BufferedReader object or some such thing (as I infer from your preamble about all of the things you have learned), the readLine() method waits for the user to press 'Enter' and then returns the String consisting of a concatenation of the sequence of characters from the keys that the user pressed before hitting the 'Enter' key.

    If the user just pressed 'Enter' and nothing else, the readLine() method returns an "empty" String, and that's what (I'm guessing) you may be looking for, when you say that the user doesn't do "anything."

    "Does not input anything" in your problem statement is defined as pressing 'Enter' and nothing else, right?

    So: Is you assignment to make a loop that waits for the user to enter some "stuff" and keep looping if the user just presses 'Enter' and nothing else?

    Then, starting with what I think I am seeing in your codelet) it could go something like this:
            BufferedReader myInput = new BufferedReader(new InputStreamReader(System.in));
    .
    .
    .
            String line;
            String blank = "";
            do {
                System.out.print("Enter an integer: ");    
                line = myInput.readLine();
                // Test to see if the line is equal to the String that you have defined as blank.
                if (/* The line is not a blank line */) { // Use the String.equals() method to test for equality
     
                   /* Do something useful with the non-blank line */
     
                }
            } while (/* The line is a blank line */); // If it's a blank line, loop back for more, otherwise terminate the loop


    Cheers!

    Z
    Last edited by Zaphod_b; October 30th, 2012 at 05:11 PM.

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