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Thread: System.out.print -align

  1. #1
    Junior Member
    Join Date
    Nov 2010
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    Default how to align last digits

    Let me present my problem on this case:

    int number = 0;
    for(int i=1; i<11; i++){
    number = (int) (Math.random()* 100);
    System.out.println(" " + number);
    Running this program in cmd, it simply prints out 10 numbers, each in new line. Their first digits are aligned.

    What am I trying to do is to align their last digits.

    I couldn't find any advanced parameters in "System.out.println" to set.
    Is there another "out-printing" method in java that I can use?

    (keep in mind, that I have to run this program in cmd)

    Any help would be very apriciated
    Last edited by juwan; November 13th, 2010 at 08:48 AM.

  2. #2
    Join Date
    Dec 2009
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    Wink Re: System.out.print -align

    This is quite simple really, you just need to check to see the value of the number and insert chars or spaces before you print the number, ie, if you have the following numbers: 4 16 100, why not make then 004, 016 and 100? Here is a quick and dirty example of this in action with comments:
    // Okay, this is an example to line up numbers so that the last
    // or least significant number is aligned, let's see how we can
    // do this in Java, eh? First, we need to declare our class name
    // or something.
    public class Align
    //Right, let's get into the main routine
        public static void main (String args [])
            // Okay, let's set up some variables:
            int eye=0;
            int number=0;
            // Here is our loop:
            for (eye=1;eye<=10;eye=eye+1)
                // Okay, we'll make the variable number a random
                // number less that 100? Or will it be less than
                // 101? I can't remember, but in some languages,
                // if you want an integer number to 100 then you
                // have to specify 101, so to be on the safe
                // side, and assuming that we want a number up to
                // 100, we'll ask for a number up to 101:
                // Right, let's start off with a space using print,
                // print will not put a line feed after it, which
                // we'll do when we've actually printed the number
                // out with 'println':
                System.out.print(" ");
                // Here are our conditions so...
                if (number<10)
                    // we'll put two digits in front of the number
                    // or...
                else if (number>=10 && number<100)
                    // we'll put one digit in front of the number
                // now, we'll print the number with a line feed after it
                // Just a note: I'm going to assume that you may replace
                // the nuaghts with spaces to align the numbers to the
                // right :-) Enjoy! Shaun Bebbington MMX
    Simple, eh?



  3. #3
    Member Darryl.Burke's Avatar
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    Mar 2010
    Madgaon, Goa, India
    Thanked 48 Times in 46 Posts

    Default Re: System.out.print -align

    Read the API for String#format(...) and PrintStream#printf(...). And you'll want to to get the details of formats from Formatter.


  4. #4
    Forum VIP
    Join Date
    Jul 2010
    Thanked 329 Times in 305 Posts

    Default Re: System.out.print -align

    Alternatively, you can use printf, which is used in C.

    When using printf, you use placeholders which you can format. The placeholder for int is %d. If you want to indicate that all numbers should have 2 spaces, you use the placeholder %2d. If you want all numbers to hold 2 spaces and have a leading zero if the space(s) in front of the number would otherwise be just an empty space, you use the placeholder %02d.

    So, if you want all of your numbers to be aligned without leading zeros, your code would look like this:

    int number = 0;
    for(int i=1; i<11; i++){
    number = (int) (Math.random()* 100);
    System.out.printf("%2d", number);

    If you want all of your numbers to be aligned with leading zeros, your code would look like this:
    int number = 0;
    for(int i=1; i<11; i++){
    number = (int) (Math.random()* 100);
    System.out.printf("%02d", number);

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