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Thread: Can someone explain to me?

  1. #1
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    Default Can someone explain to me?

    Can someone explain the coding in bold to me? I don't understand how to get 40 10 20 30.

    public class Rotater {


    public static void main(String[] args) {


    int a = 10, b = 20, c = 30, d = 40;
    int temp;

    temp = d;
    d = c;
    c = b;
    b = a;
    a = temp;



    System.out.println("before rotation: 10 20 30 40");
    System.out.println("after rotation: " + a + " " + b + " " + c + " " + d);


    }
    }

  2. The Following User Says Thank You to unleashed-my-freedom For This Useful Post:

    roronoaz (July 3rd, 2012)


  3. #2
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    Default Re: Can someone explain to me?

    Hello unleashed-my-freedom!
    What is your question? You use the temp variable to rotate the values of your "basic" variables (a,b,c,d). So, you give every variable the value of the next (or previous) variable* . The additional variable (temp) is used for keeping the first basic variables's value and don't loose it.

    *in your case next and previous don't have an actual meaning because the variables are not ordered but suppose they are (a-b-c-d)

    Hope I was clear.

  4. #3
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    Default Re: Can someone explain to me?

    At first, I had 10 20 30 40
    But the temp, I had 40 10 20 30.
    So you mean if I use temp, the number will (in this case) increase by 1 position?

  5. The Following User Says Thank You to unleashed-my-freedom For This Useful Post:

    roronoaz (July 3rd, 2012)

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    Default Re: Can someone explain to me?

    After the rotation the values have moved one step forward with the last value going to the first variable (like a cycle).
    after initialization
    a   b   c   d    temp
    10  20  30  40      -
     
     
    temp  = d;
    a   b   c   d    temp
    10  20  30  40      40
     
     
    d = c;
    a   b   c  d    temp
    10  20  30  30   40
     
     
    c = b;                   
    a   b   c   d     temp
    10  20  20  30      40
     
     
    b = a;                 
    a   b   c   d     temp
    10  10  20  30      40
     
     
    a = temp;           
    a   b   c   d     temp
    40  10  20  30      40
    Hope this helps.

  7. The Following 2 Users Say Thank You to andreas90 For This Useful Post:

    roronoaz (July 3rd, 2012), unleashed-my-freedom (July 3rd, 2012)

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    Default Re: Can someone explain to me?

    so we use temp just to increase the order by 1?

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    Default Re: Can someone explain to me?

    Quote Originally Posted by unleashed-my-freedom View Post
    so we use temp just to increase the order by 1?
    We use temp because otherwise you would loose a value. Think like you have two cups (A and B) in two positions (1 and 2 respectively) that each of them can place only one cup and you can carry only one cup in your hands. Now, if you want to exchange positions between cups you start like this:
    take cup A and put it in position 1. But then you have to throw away cup B(because you can't have two cups in you a position or in your hands).
    Therefore you need a new assisting position (3).
    Then you put
    1) cup A to position 3 - now position 1 is empty
    2) cup B to position 1 - now position 2 is empty
    3) cup A to position 2

    So, temp is the assisting position.

    Hope that makes sense.

  10. The Following User Says Thank You to andreas90 For This Useful Post:

    roronoaz (July 3rd, 2012)

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