COMP SCI 101 - Centering Fields Using Printf

Question

I am creating a Celsius to Fahrenheit conversion table using the printf function.

In my notes, I see that I should be able to center the output using the ^ flag immediately after the % for printf. However, Netbeans always gives me an error message when I run the program.

I was wondering if anybody can help me center my output. My code is as follows.

I have looked through questions that have already been answered. However, they do not correspond with what I was taught in class thus far and as such - I cannot use it.

Any help would be greatly appreciated.

public class CelsToFahrTable {

/**
 * Main argument prints a Celsius to Fahrenheit conversion table
 * using integer Celsius degrees from 0 to 40
 */
public static void main(String[] args) 
{
    // declare variables
    double Cels; //control variable (Celsius Temperature)

    System.out.printf("%10s\t%10s%n", "Celsius", "Fahrenheit"); 
    //prints headers Celsius and Fahrenheit at the top to signify what the data
    //below means. Celsius should take up 10 columns then tab to Fahrenheit
    //which again takes up 10 columns

    for ( Cels = 0; Cels <= 40; Cels++)
        //creates count-controlled loop using for statement
        //Cels initialized to 0, continues expression until 40 and increments
        //by 1 degree each time

        System.out.printf("%10.0f%10.1f%n", Cels, 1.8*Cels+32.0);
    //creates table showing Celsius temperature followed by its corresponding
    //Fahrenheit temperature. Celsius temp is 10 columns with no decimals.  
    //Fahrenheit temp is 10 columns with a 1 decimal precision.

    //Note: I tried to center each field using "^" but it gave me an error 
    //every time

}//end main

The "^" would be placed in the final:

System.out.printf ("%^10.0f%^10.1f%n", Cels, 1.8*Cels+32.0"

----However when I type that code I get an error in Netbeans.

The "^" would be placed in the final: System.out.printf ("%^10.0f%^10.1f%n", Cels, 1.8*Cels+32.0" ----However when I type that code I get an error in Netbeans. — zhughes3, Sep 29 '13 at 17:59
Don't blindly follow your notes. Go read the `printf` format rules in the [`Formatter` class javadoc](http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html) — Sotirios Delimanolis, Sep 29 '13 at 18:03
I did and it does not list any ways to center these fields @SotiriosDelimanolis — zhughes3, Sep 29 '13 at 18:03
Center them on what? The `System.out` is standard output, usually the console. How can Java know its display size? — Sotirios Delimanolis, Sep 29 '13 at 18:04
@SotiriosDelimanolis I want to center them underneath their headers. In this example, they would be center under "Celsius" and "Fahrenheit" — zhughes3, Sep 29 '13 at 18:06
[^ is not a valid printf flag](http://stackoverflow.com/questions/8468467/how-to-center-a-text-using-printf-with-flag-in-java). — AbdullahC, Sep 29 '13 at 18:09

score 0 · Accepted Answer · edited May 23 '17 at 11:56

0

If you look through the Formatter javadoc, Java does not have a flag to center the output of printf, and there is no ^ flag.

Your notes are probably referring to the Lava library, which comes with "an advanced" Java port of the C printf function. As specified in the Lava specification under the section on flags, ^ is the flag for centering output.

As specified elsewhere on SO, you can use the StringUtils.center method from the Apache Commons Lang Library, or devise a method of your own.

edited May 23 '17 at 11:56

Community

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answered Sep 29 '13 at 18:32

AbdullahC

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Thank you very much for your information. Through this post, I learned that ^ is not a valid flag. Since, my professor has not taught us how to use the StringUtils.center method, I won't use it. But I did tinker around with the column width in the final printf I used in my code to make it appear centered. And it looks pretty good. – zhughes3 Sep 29 '13 at 19:07

COMP SCI 101 - Centering Fields Using Printf

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