Java Format Specifier

In this chapter you will learn:

1. What is Format Specifier
2. What are the specifiers for Java Formatter class
3. Example - Java Format Specifier
4. Example - Unknown Format Conversion Exception
5. How to use %n and %% specifiers to escape new line and percentage
6. Example - The following code combines the %n, %d %% to display file copy progress information

Description

The format() method accepts a wide variety of format specifiers. When an uppercase specifier is used, then letters are shown in uppercase. Otherwise, the upper- and lowercase specifiers perform the same conversion.

Specifier List

The following table shows the format specifiers:

If the argument doesn't match the type-checks, an IllegalFormatException is thrown.

Example

Java Format Specifier

import java.util.Calendar;
import java.util.Formatter;
/*w  w  w  .  j  ava2 s .  c om*/
public class Main {
  public static void main(String args[]) {
    Formatter fmt = new Formatter();

    fmt = new Formatter();
    System.out.println(fmt.format("%s gap filler %d %f", "Astring", 10, 12.3)); 
  
  }
}

You can obtain a reference to the underlying output buffer by calling out(). It returns a reference to an Appendable object.

The code above generates the following result.

Example 2

Unknown Format Conversion Exception

import java.util.Date;
import java.util.Formatter;
/*from w w w. java2s.c o  m*/
public class Main {
  public static void main(String args[]) {
    Formatter fmt = new Formatter();

    fmt.format("%t", new Date());
    System.out.println(fmt);
  }
}

The code above generates the following result.

Example 3

The %n and %% format specifiers escape sequences. The %n inserts a newline. The %% inserts a percent sign.

You can use the standard escape sequence \n to embed a newline character. Here is an example that demonstrates the %n and %% format specifiers:

import java.util.Formatter;
/*w w w . j  a v  a 2  s .  c o  m*/
public class Main {
  public static void main(String args[]) {
    Formatter fmt = new Formatter();
    fmt.format("line%nline %d%% complete", 88);
    System.out.println(fmt);
  }
}

The output:

Example 4

The following code combines the %n, %d %% to display file copy progress information.

import java.util.Formatter;
//from w  ww .jav  a2 s.c  om
public class Main {
  public static void main(String args[]) {
    Formatter fmt = new Formatter();
    fmt.format("Copying file%nTransfer is %d%% complete", 88);
    System.out.println(fmt);

  }
}

The output:

Next chapter...

What you will learn in the next chapter:

1. What is Format Specifier
2. How and when to use Uppercase Option for Java Formatter
3. How to uppercase hexadecimal
4. How to uppercase e symbol

Java Format Specifier