Align printf output in Java

Question

I need to display a list of items with their prices from an array and would like to align the prices. I almost have it working but needs improvements. Below is the code and the output. Any ideas how to make all prices aligned? So far some work but some don't.

//for loop
System.out.printf("%d. %s \t\t $%.2f\n",
                i + 1, BOOK_TYPE[i], COST[i]);

output:

1. Newspaper         $1.00
2. Paper Back        $7.50
3. Hardcover book        $10.00
4. Electronic book       $2.00
5. Magazine          $3.00

Cas

docs.oracle.com/javase/7/docs/api/java/util/Formatter.html shows how you can align your output. For example: formatter.format(Locale.FRANCE, "e = %+10.4f", Math.E); where 10 is the number of "spaces" between the equal sign and the number being printed and 4 is the number of decimal places. – Driggers

Answer 1

You can try the below example. Do use '-' before the width to ensure left indentation. By default they will be right indented; which may not suit your purpose.

System.out.printf("%2d. %-20s $%.2f%n",  i + 1, BOOK_TYPE[i], COST[i]);

Format String Syntax: http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax

Formatting Numeric Print Output: https://docs.oracle.com/javase/tutorial/java/data/numberformat.html

PS: This could go as a comment to DwB's answer, but i still don't have permissions to comment and so answering it.

Horde

Answer 2

A simple solution that springs to mind is to have a String block of spaces:

String indent = "                  "; // 20 spaces.

When printing out a string, compute the actual indent and add it to the end:

String output = "Newspaper";
output += indent.substring(0, indent.length - output.length);

This will mediate the number of spaces to the string, and put them all in the same column.

Cates

Seeing answers like this makes me wish Java's String had padLeft, padRight, etc like other programming languages' standard libraries... – Faydra

Java does have StringUtils.leftPad() and StringUtils.rightPad(). these are part of Apache Commons Lang. – Bernard

Answer 3

Format specifications for printf and printf-like methods take an optional width parameter.

System.out.printf( "%10d. %25s $%25.2f\n",
                   i + 1, BOOK_TYPE[i], COST[i] );

Adjust widths to desired values.

Bernard

First off, don't call someone lazy without know anything about that person. Second, I am a Java beginner but I did read about printf and I know the %10d will print 10 spaces before the variable. Now Mr. Know-it-all-and-not-lazy, your code is nowhere near what I need. If you read my question, I need to have left alignment, except the space after the second variable needs to change (not constant) so the third variable is also aligned. Thanks anyways. Good day. – Cas

if you had read the printf docs then you would know that %10d specifies a field width of 10 and %010d specifies zero left padded field with width 10. consider reading the docs. – Bernard

reading the docs will show you that a - as a flag will left justify the field. ex %-10d – Bernard

Answer 4

Here's a potential solution that will set the width of the bookType column (i.e. format of the bookTypes value) based on the longest bookTypes value.

public class Test {
    public static void main(String[] args) {
        String[] bookTypes = { "Newspaper", "Paper Back", "Hardcover book", "Electronic book", "Magazine" };
        double[] costs = { 1.0, 7.5, 10.0, 2.0, 3.0 };

        // Find length of longest bookTypes value.
        int maxLengthItem = 0;
        boolean firstValue = true;
        for (String bookType : bookTypes) {
            maxLengthItem = (firstValue) ? bookType.length() : Math.max(maxLengthItem, bookType.length());
            firstValue = false;
        }

        // Display rows of data
        for (int i = 0; i < bookTypes.length; i++) {
            // Use %6.2 instead of %.2 so that decimals line up, assuming max
            // book cost of $999.99. Change 6 to a different number if max cost
            // is different
            String format = "%d. %-" + Integer.toString(maxLengthItem) + "s \t\t $%9.2f\n";
            System.out.printf(format, i + 1, bookTypes[i], costs[i]);
        }
    }
}

Isomer

Just brilliant, I don't know how I didn't think of this. Thanks! – Linis

Answer 5

You can refer to this blog for printing formatted coloured text on console

https://javaforqa.wordpress.com/java-print-coloured-table-on-console/

public class ColourConsoleDemo {
/**
*
* @param args
*
* "\033[0m BLACK" will colour the whole line
*
* "\033[37m WHITE\033[0m" will colour only WHITE.
* For colour while Opening --> "\033[37m" and closing --> "\033[0m"
*
*
*/
public static void main(String[] args) {
// TODO code application logic here
System.out.println("\033[0m BLACK");
System.out.println("\033[31m RED");
System.out.println("\033[32m GREEN");
System.out.println("\033[33m YELLOW");
System.out.println("\033[34m BLUE");
System.out.println("\033[35m MAGENTA");
System.out.println("\033[36m CYAN");
System.out.println("\033[37m WHITE\033[0m");

//printing the results
String leftAlignFormat = "| %-20s | %-7d | %-7d | %-7d |%n";

System.out.format("|---------Test Cases with Steps Summary -------------|%n");
System.out.format("+----------------------+---------+---------+---------+%n");
System.out.format("| Test Cases           |Passed   |Failed   |Skipped  |%n");
System.out.format("+----------------------+---------+---------+---------+%n");

String formattedMessage = "TEST_01".trim();

leftAlignFormat = "| %-20s | %-7d | %-7d | %-7d |%n";
System.out.print("\033[31m"); // Open print red
System.out.printf(leftAlignFormat, formattedMessage, 2, 1, 0);
System.out.print("\033[0m"); // Close print red
System.out.format("+----------------------+---------+---------+---------+%n");
}

Radbun

The blog's gone, but your formatting string examples are still useful. Thanks. – Arv