String formatting example

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