Two methods of the System.out object

System.out.printf(formatString);
or:
System.out.printf(formatString, argumentList);

where formatString is a string specifying the format of the output, and

argumentList is a list of arguments that consists of
constant values, variables, or expressions.

If there is more than one argument in argumentList,
then the arguments are separated with commas.

Example:

System.out.printf("Hello there!");
	consists of only the format string, and the statement:

System.out.printf("There are %.2f inches in %d centimeters.%n",
					centimeters / 2.54, centimeters);
 	consists of both the format string and argumentList

• %.2f and %d are called format specifiers
• By default, there is a one-to-one correspondence between format specifiers and the arguments in argumentList
• The first format specifier %.2f is matched with the first argument, which is the expression centimeters / 2.54
• The second format specifier %d is matched with the second argument, which is centimeters
• The format specifier %n positions the insertion point at the beginning of the next line.

A format specifier for general, character, and numeric types has the following syntax:

%[argument_index$][flags][width][.precision]conversion

• The expressions in square brackets are optional; they may or may not appear in a format specifier
• The option argument_index is a (decimal) integer indicating the position of the argument in the argument list
• The first argument is referenced by "1$", the second by "2$", etc.
• The option flags is a set of characters that modify the output format
• The option width is a (decimal) integer indicating the minimum number of characters to be written to the output
• The option precision is a (decimal) integer usually used to restrict the number of characters
• The required conversion is a character indicating how the argument should be formatted

Here are some of Java's supported conversions

Code that formats the output of decimal numbers.

public class printf1
{
    public static void main(String[] args)
    {
        double x = 15.674;                              //Line 1
        double y = 235.73;                           	//Line 2
        double z = 9525.9864;                			//Line 3

        System.out.println("Line 4: The values of x, "
        				 + "y, and z with two decimal "
                         + "places."); 					//Line 4
        System.out.printf("Line 5: x = %.2f %n", x);	//Line 5
        System.out.printf("Line 6: y = %.2f %n", y);	//Line 6
        System.out.printf("Line 7: z = %.2f %n", z);	//Line 7

        System.out.println("Line 8: The values of x, "
        				 + "y, and z with three decimal "
                         + "places."); 					//Line 8
        System.out.printf("Line 9: x = %.3f %n", x);	//Line 9
        System.out.printf("Line 10: y = %.3f %n", y);	//Line 10
        System.out.printf("Line 11: z = %.3f %n", z);	//Line 11
    }
}

Code that formats the output using the format specifier.

public class printf2
{
    public static void main(String[] args)
    {
        int num = 763;                               //Line 1
        double x = 658.75;                           //Line 2
        String str = "Java Program.";                //Line 3

        System.out.println("1234567890123456789"
                         + "01234567890"); 			//Line 4
        System.out.printf("%-5d%-7.2f%-15s ***%n",
                           num, x, str);             //Line 5 flag="-" to output left justified.
        System.out.printf("%-15s%-6d%-9.2f ***%n",
                           str, num, x);             //Line 6
        System.out.printf("%-8.2f%-7d%-15s ***%n",
                           x, num, str);             //Line 7

        System.out.printf("num = %-5d ***%n", num);  //Line 8
        System.out.printf("x = %-10.2f ***%n", x);   //Line 9
        System.out.printf("str = %-15s ***%n", str); //Line 10
        System.out.printf("%-10s%-7d ***%n",
                          "Program No.", 4);         //Line 11
    }
}