Align printf output in Java

问题

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. Thanks in advance.

//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

回答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.

回答2:

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.

回答3:

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.

回答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]);
        }
    }
}

回答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");
}

来源：https://stackoverflow.com/questions/15961130/align-printf-output-in-java

标签

java

alignment

printf

text-align