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Thread: Help with Arrays!

  1. #1
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    Question Help with Arrays!

    Hey guys! I'm fairly new to java. For my course at uni I've got to design a caeser box that will encrypt a word and decrypt it. I pretty certain I've got the logic behind it so I won't need someone to give me the full code haha that would be cheating anyway. I like a challenge. Anyway.
    I've started my code by reading the string, I've eliminated white spaces and its all lower case. After that I put the string in a char array with a total length of the string without whitespaces. after this I declared a grid with dimensions of x*x where x is the closest root of the length of the string without whitespaces.
    So upto now its all good but this is where the problem starts ...
    I've done 2 for loops to create the grid and then I'm increasing the rows and columns by 1 (ofc) and the values of each grid is equal to the elements of my char array that contains the string.
    this might seem messy but I'll paste the problematic code part:
    for(int row = 0; row<plainTextGrid.length; row++){
        		for(int column = 0; column <plainTextGrid.length; column++){
        			plainTextGrid[row][column]= plainTextArray[0];// this is where I want to set each element to a position on the grid. plainTextGrid is the grid, and plainTextArray is the array
     
     
        			System.out.print(plainTextGrid[row][column] + " ");
        			}
     
        			System.out.println();
        		}
    My question is how can I increase each element of the char array by 1.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Help with Arrays!

    how can I increase each element of the char array by 1.
    You can do normal math with char values: 'a' + 1 = 'b'
    If you don't understand my answer, don't ignore it, ask a question.

  3. The Following User Says Thank You to Norm For This Useful Post:

    le pencil (April 12th, 2013)

  4. #3
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    Default Re: Help with Arrays!

    Quote Originally Posted by Norm View Post
    You can do normal math with char values: 'a' + 1 = 'b'
    I don't actually get what you are trying to say. My char array is in the two for loops, I want to increment the value of it until it reaches the last char in the array. so for example I could do this:
    plainTextGrid[row][column]= plainTextArray[0];
    plainTextArray[0]=plainTextArray[1];
    plainTextArray[1]=plainTextArray[2];
    //etc...

    yeah so basically thats untidy and not useful for my situation

    --- Update ---

    Man Norm you are the best I can't believe how easy of a fix that was!!! cheers!

  5. #4
    Super Moderator Norm's Avatar
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    Default Re: Help with Arrays!

    Please explain what you mean by " increment the value"
    x= x+1 // increments the value of x by 1

    The code at the end of the post looks like it is shifting the elements to the left by one slot. Does the shifting wrap around at the end: first element goes in last slot?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Help with Arrays!

    So what I did was add an int above the for loops
    int a = 32;
        	for(int row = 0; row<plainTextGrid.length; row++){
        		for(int column = 0; column <plainTextGrid.length; column++){
     
        			plainTextGrid[row][column]= plainTextArray[32-a];
        			a--;
     
     
        			System.out.print(plainTextGrid[row][column] + " ");
        			}
     
        			System.out.println();
        		}

    and output :
    a l o n g t
    i m e a g o
    , i n a g a
    l a x y f a
    r , f a r a
    w a y Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 33
    at CaesarBox.encrypt(CaesarBox.java:30)
    at CaesarBox.main(CaesarBox.java:8)

  7. #6
    Super Moderator Norm's Avatar
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    Default Re: Help with Arrays!

    ArrayIndexOutOfBoundsException: 33
    Looks like a went to -1
    33 = 32 - (-1)
    How many times does the inner loop execute?

    The code needs to check that the index is in bounds.
    If you don't understand my answer, don't ignore it, ask a question.

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