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  1. #1
    TheWhopper is offline Member
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    Default Help with "Head First Java" quiz

    Having a difficult time (just started learning Java a couple days ago) trying to figure out how the code below gets the following output

    Java Code:
    00 11 21 32 42
    I couldn't figure it out just by looking through the book, but I verified the output above is correct after I tested in Eclipse.

    Java Code:
    class Test {
      public static void main(Strings [] args) {
       int x = 0;
       int y = 0; 
       while ( x < 5 ) {
          y = x - y;
          System.out.print(x + "" + y +" ");
          x = x + 1;
       }
      }
    }
    Here is the actual page in the book "Head First Java"

    Head first Java - Google Books

    Any ideas how the code above produces this output?

    Java Code:
    00 11 21 32 42

    Many thanks!!
    Last edited by TheWhopper; 06-04-2011 at 04:27 AM.

  2. #2
    sunde887's Avatar
    sunde887 is offline Moderator
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    What exactly dont you understand?(assuming the u in the print is meant to be a y). Why not try tracing the loop one step at a time. Find out what x and y are before you reach the print statement by hand.

  3. #3
    TheWhopper is offline Member
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    (replaced the 'u' with a 'y') I'm mainly stuck due to the quotations. I have a decent grasp of the 'while loop', it's just that part I don't know enough of. If you can give me some input regarding the quotations please....
    Last edited by TheWhopper; 06-04-2011 at 04:41 AM.

  4. #4
    sunde887's Avatar
    sunde887 is offline Moderator
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    The quotes are used to convert the ints to strings, once they are hanged to strings all the +'s are overloaded to be string concatenation, the blank quotes(""), just makes the numbers appear next to eachother, the spaced quotes(" ") add a space between the first number pair and the second.

  5. #5
    TheWhopper is offline Member
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    Thanks sunde887!! I just learned several things (some fell into place) just by the information you provided!

  6. #6
    sunde887's Avatar
    sunde887 is offline Moderator
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    Your welcome, glad I helped you out.

  7. #7
    DarrylBurke's Avatar
    DarrylBurke is offline Member
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    Read about the specifics of the String concatenation operator here:
    Expressions

    db

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