Print Formatting in Columns trouble

[Inventor22]

Having written a program that gets the mouses coordinates and the different RGB values of the pixel at those coordinates I then sought after recording the data in a text file. Ideally for easy viewing later I wanted each category separated into different columns, something like pic1 (smaller image).

Instead, I am getting results like pic2.

In attempt to format the text into columns, i just used tabs, however this does not seem to work properly... here is the code just for the printing (I am outputting to a text file):

	    record.println("X: " + X
		    + "\tY: " + Y
		    + "\tR: " + red
		    + "\tG: " + green
		    + "\tB: " + blue);

I did look at the Formatter class, however I found nothing of use.

I do know that in the Turing language you can format a print statement like so: ('put' is the Turing equivalent of 'System.out.println();')

put "hello":6
put "you"

And the output will display as "hello you" because hello is 5 characters long, but you specified the first put (print) statement to be 6 characters long.

Any ideas on how to solve this problem?
Thanks.

[JosAH]

I did look at the Formatter class, however I found nothing of use.

Read the API documentation, don't just look at it; even better: read the API documentation for the System.printf( ... ) method; it leads you to that same Formatter class which has the answer.

kind regards,

Jos

[Inventor22]

Your absolutely right. I should have read the API docs better, (although it is 3 am...:rolleyes:).
I did look over the right thing, just misinterpreted what it did. I thought that for example printf("%1d",5); would have printed something like " 5" and not just "5".

I got everything working with the following code:

	    record.printf("X: %-5d " +
		    "Y: %-4d " +
		    "R: %-4d " +
		    "G: %-4d " +
		    "B: %-4d\n",X,Y,red,green,blue);

Although in the meantime just after posting the first post in this thread, I did come up with a crude fix for my problem by making a small method to add any necessary spaces...

    public String format(int num, int length) {
	String f = Integer.toString(num);
	for (int i = 0; i < length; i++) {
	    try {
		f.charAt(i); // check to see if there is anything at the current
		// index position
	    } catch (Exception e) {
		f = f + " "; // if not, add a space.
	    }
	}
	return f;
    }

[JosAH]

Your absolutely right. I should have read the API docs better, (although it is 3 am...:rolleyes:).
I did look over the right thing, just misinterpreted what it did. I thought that for example printf("%1d",5); would have printed something like " 5" and not just "5".

I got everything working with the following code:

	    record.printf("X: %-5d " +
		    "Y: %-4d " +
		    "R: %-4d " +
		    "G: %-4d " +
		    "B: %-4d\n",X,Y,red,green,blue);

Although in the meantime just after posting the first post in this thread, I did come up with a crude fix for my problem by making a small method to add any necessary spaces...

    public String format(int num, int length) {
	String f = Integer.toString(num);
	for (int i = 0; i < length; i++) {
	    try {
		f.charAt(i); // check to see if there is anything at the current
		// index position
	    } catch (Exception e) {
		f = f + " "; // if not, add a space.
	    }
	}
	return f;
    }

That fix is indeed too crude: Exceptions are thrown each time you are peeking beyond the length of that String f and then you add one single space to it. Better use StringBuilders for that purpose:

public String format(int num, int length) {
   StringBuilder sb= new StringBuilder(length);

   sb.append(num);
   while (sb.length() < length)
      sb.append(' ');
   return sb.substring(0, length);
}

This method basically does the same as your version but it is much cheaper in execution time and memory.

kind regards,

Jos

[Inventor22]

yea, I wasn't exactly thinking when I came up with that one... :P

I also found that this worked as well:

    public static String format2(int num, int length) {
	String f = Integer.toString(num);
	while(f.length()<length){
	    f = f.concat(" "); // would  f = f + ' ';  be more efficient?
	}
	return f;
    }

I don't know why I didn't think of that one to begin with...
Would the above method be any less efficient than using your method with a StringBuilder?

Thanks for all the help.:D

[JosAH]

yea, I wasn't exactly thinking when I came up with that one... :P

I also found that this worked as well:

    public static String format2(int num, int length) {
	String f = Integer.toString(num);
	while(f.length()<length){
	    f = f.concat(" "); // would  f = f + ' ';  be more efficient?
	}
	return f;
    }

I don't know why I didn't think of that one to begin with...
Would the above method be any less efficient than using your method with a StringBuilder?

Thanks for all the help.:D

Adding something to a String involves StringBuffers; the compiler does that when it sees you adding two Strings or a String and something else. It creates a new StringBuffer for each addition; we (the humans) can do better than that (see my first example) and use one StringBuilder for the entire process. The compiler is a bit near sighted so it generates a bit stupid code ...

kind regards,

Jos

[Inventor22]

Good to know! Thanks:)