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Formatter class

In this chapter you will learn:

  1. What is Formatter class for
  2. Formatting Basics

What is Formatter class for

Formatter class outputs the formatted output. It can format numbers, strings, and time and date. It operates in a manner similar to the C/C++ printf() function.

Formatting Basics

The most commonly used format function is:

Formatter format(String fmtString, Object ... args)

The fmtSring consists characters that are copied to the output buffer and the format specifiers.

A format specifier begins with a percent sign followed by the format conversion specifier. For example, the format specifier for floating-point data is

%f

The format specifiers and the arguments are matched in order from left to right. For example, consider this fragment:

import java.util.Formatter;
// j av a  2  s. c  o m
public class Main {
  public static void main(String args[]) {
    Formatter fmt = new Formatter();
    fmt.format("%s gap filler %d %f", "Astring", 10, 12.3); 
    System.out.println(fmt.out());
  }
}

The output:

In this example, the format specifiers, %s, %d, and %f, are replaced with the arguments that follow the format string. %s is replaced by "Astring", %d is replaced by 10, and %f is replaced by 12.3. %s specifies a string, and %d specifies an integer value. %f specifies a floating-point value. All other characters are simply used as-is.

Next chapter...

What you will learn in the next chapter:

  1. What are the specifiers for Java Formatter class
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