Aligning decimal output in Java

[seamus_padraig]

How dow you align decimal numbers when outputting them to the console in Java?

 

[Mainframeguy]

dunno about Java especially, but typicaly this will involve casting the variable from a numeric type into a string type, depending on the sophistication of the language and implementation this may be enough, or you may need to apply a mask or somesuch to specify the alignment required or to remove leading/trailing zeros.

Why not give an example of your need? IE do you want them aligned like this?

123.45
__1.023

(for _ ready space!) or in some other way?

Welcome to OSNN

 

[seamus_padraig]

Yeah, your example is exactly what I'm trying to do. I want to right-align a series of dollar figures on the decimal point for output. Java has formatting classes for all the other stuff (commas, dollar signs, etc.); just nothing for right-alignment on the decimal.

 

[X-Istence]

Go poke Geffy, he is our resident Java expert.

 

[Geffy]

Well there isnt anything useful for doing this in the Interger wrapper class

 

[Geffy]

/**
 * Number Formatting, either by the length of the numeric string
 * or by the length from the first number to the decimal point.
 *
 * @author Geoffrey Garside <java AT stealth-ninja DOT co DOT uk>
 * @version 1.0, 2004/12/11
 */

public class NumberFormat {
    public static String[] alignByLength(final int [] numbers) {
        // Create Similar array but for strings
        String [] formatted = numbersToStrings(numbers);
        
        int length = maxLength(formatted);
        formatted = appendSpaces(formatted, length);
        
        return formatted;
    }
    
    public static String[] alignByLength(final double [] numbers) {
        // Create Similar array but for strings
        String [] formatted = numbersToStrings(numbers);
        
        int length = maxLength(formatted);
        formatted = appendSpaces(formatted, length);
        
        return formatted;
    }
    
    public static String[] alignByLength(final float [] numbers) {
        // Create Similar array but for strings
        String [] formatted = numbersToStrings(numbers);
        
        int length = maxLength(formatted);
        formatted = appendSpaces(formatted, length);
        
        return formatted;
    }
    
    public static String[] alignByDecimal(final double [] numbers) {
        // Create Similar array but for strings
        String [] formatted = numbersToStrings(numbers);
        
        int length = maxLength(formatted, '.');
        formatted = appendSpaces(formatted, length);
        
        return formatted;
    }
    
    public static String[] alignByDecimal(final float [] numbers) {
        // Create Similar array but for strings
        String [] formatted = numbersToStrings(numbers);
        
        int length = maxLength(formatted, '.');
        formatted = appendSpaces(formatted, length);
        
        return formatted;
    }
    
    private static String[] appendSpaces(String[] strings, final int length) {
        // ok, now we need to add some spaces to the beginning
        // of each number so that they should all align properly
        for (int i = 0; i < strings.length; i++) {
            if (strings[i].length() < length) {
                int difference = length - strings[i].length();
                
                strings[i] = spaces(difference) + strings[i];
            }
        }
        
        return strings;
    }
    
    private static String spaces(final int length) {
        StringBuffer spaces = new StringBuffer();
        for (int i = 0; i < length; i++) {
            spaces.append(" ");
        }
        
        return spaces.toString();
    }
    
    private static int maxLength(final String[] strings, final char find) {
        int length = 0;
        for (int i = 0; i < strings.length; i++) {
            if (strings[i].indexOf(find) > length) {
                length = strings[i].indexOf(find);
            }
        }
        
        return length;
    }
    
    private static int maxLength(final String[] strings) {
        // lets find the longest number
        int length = 0;
        for (int i = 0; i < strings.length; i++) {
            if (strings[i].length() > length) {
                length = strings[i].length();
            }
        }
        
        return length;
    }
    
    private static String[] numbersToStrings(final int [] numbers) {
        // Create Similar array but for strings
        String [] strings = new String[numbers.length];
        
        for (int i = 0; i < strings.length; i++) {
            strings[i] = ""+ numbers[i];
        }
        
        return strings;
    }
    
    private static String[] numbersToStrings(final double [] numbers) {
        // Create Similar array but for strings
        String [] strings = new String[numbers.length];
        
        for (int i = 0; i < strings.length; i++) {
            strings[i] = ""+ numbers[i];
        }
        
        return strings;
    }
    
    private static String[] numbersToStrings(final float [] numbers) {
        // Create Similar array but for strings
        String [] strings = new String[numbers.length];
        
        for (int i = 0; i < strings.length; i++) {
            strings[i] = ""+ numbers[i];
        }
        
        return strings;
    }
}

something I just whipped up, I havent tested it beyond compilation. I also cant be arsed to comment it properly right now, but I might do that later