Formatting Strings and Numbers

The program below is self-explanatory. It shows how to format a string in Java using the format method of the String class and System.out.printf. Enter the program below in Eclipse and observe what it does. You can use this page as a reference for formatting strings in future assignments.

import java.util.Date;
/**
 * Java program to demonstrate How to format String in Java by using
 * format() method of String class and printf() method of OutputStream in Java.
 * String.format() is very powerful and not only can format String but numbers
 * and Date in Java
 */
public class StringFormat{

 public static void main(String args[]){ 

 //simple example of formatted string in Java
 //%d is used to format decimals like integers
 //position of argument is the order in which they appear in source String
 // e.g here 40021 will replace first %d and 3000 will replace second %d.
 String formattedString = String.format("Order with OrdId : %d and Amount: %d is missing", 40021, 3000);

 System.out.println(formattedString);

 System.out.printf("Order with OrdId : %d and Amount: %d is missing \n", 40021, 3000);

 //%s is used to denote String arguments in formatted String
 String str = String.format("Hello %s", "Raj");
 System.out.println(str);

 //if argument is not convertible into specified data type than
 //Formatter will throw following java.util.IllegalFormatConversionException
 //e.g. specifying %d and passing 3.0
 //str = String.format("Number %d", 3.0);

 //common meta characters used in String.format() and
 //System.out.printf() method: %s - String , %d - decimal integer
// %f - float %tD - date as MM/dd/yy while %td is day %tm is month
 // and %ty is 2 digit year while %tY is four digit year

 //Formatting date in String format method - date in MM/dd/yy
 str = String.format("Today is %tD", new Date());
 System.out.println(str);

 Date today = new Date();
 System.out.printf("Date in dd/mm/yy format %td/%tm/%ty %n", today,today,today );

 // date as July 25, 2012, difference between %td and %te is that
 // %td use leading zero while %te doesn't
 System.out.printf("Today is %tB %te, %tY %n", today,today,today,today);

 //adding leading zero in numbers using String format,
 //%d is for decimal, 8 specify formatted number should be 8 digit and 0 specify use
 //leading zero, default is space, so if you don't specify leading
 // character space will be used.
 System.out.printf("Amount : %08d %n" , 221);

 //printing positive and negative number using String format
 //+ sign for positive, - for negative and %n is for new line
 System.out.printf("positive number : +%d %n", 1534632142);
 System.out.printf("negative number : -%d %n", 989899);

 //printing floating point number with System.format()
 System.out.printf("%f %n", Math.E);

 //3 digit after decimal point
 System.out.printf("%.3f %n", Math.E);

 //8 charcter in width and 3 digit after decimal point
 System.out.printf("%8.3f %n", Math.E);

 //adding comma into long numbers
 System.out.printf("Total %,d messages processed today", 10000000);
 }

}

String formatting codes

Integer formatting codes