Other Conversion Characters

The remaining conversion characters are b, B, h, H, % and n. These are described in Fig. 28.10.

Figure 28.10. Other conversion specifiers.

Conversion character	Description
b or B	Print "true" or "false" for the value of a boolean or Boolean. These conversion characters can also format the value of any reference. If the reference is non-null, "TRue" is output; otherwise, "false" is output. When conversion character B is used, the output is displayed in uppercase letters.
h or H	Print the string representation of an object's hash code value in hexadecimal format. If the corresponding argument is a null reference, "null" is printed. When conversion character H is used, the output is displayed in uppercase letters.
%	Print the percent character.
n	Print the platformspecific line separator (e.g., on Windows or on UNIX/LINUX).

Lines 910 of Fig. 28.11 use %b to print the value of boolean values false and TRue. Line 11 associates a String to %b, which returns true because it is not null. Line 12 associates a null object to %B, which displays FALSE because test is null. Lines 1314 use %h to print the string representations of the hash code values for strings "hello" and "Hello". These values could be used to store or locate the strings in a Hashtable or HashMap (both discussed in Chapter 19, Collections). Note that the hash code values for these two strings differ because one string starts with a lowercase letter and the other starts with an uppercase letter. Line 15 uses %H to print null in uppercase letters. The last two printf statements (lines 1617) use %% to print the % character in a string and %n to print a platformspecific line separator.

Figure 28.11. Using the b, B, h, H, % and n conversion characters.

(This item is displayed on page 1336 in the print version)

 1 // Fig. 28.11: OtherConversion.java
 2 // Using the b, B, h, H, % and n conversion characters.
 3
 4 public class OtherConversion
 5 {
 6 public static void main( String args[] )
 7 {
 8 Object test = null;
 9 System.out.printf( "%b
", false );
10 System.out.printf( "%b
", true );
11 System.out.printf( "%b
", "Test" );
12 System.out.printf( "%B
", test );
13 System.out.printf( "Hashcode of "hello" is %h
", "hello" );
14 System.out.printf( "Hashcode of "Hello" is %h
", "Hello" );
15 System.out.printf( "Hashcode of null is %H
", test );
16 System.out.printf( "Printing a %% in a format string
" );
17 System.out.printf( "Printing a new line %nnext line starts here" );
18 } // end main
19 } // end class OtherConversion

 

false
true
true
FALSE
Hashcode of "hello" is 5e918d2
Hashcode of "Hello" is 42628b2
Hashcode of null is NULL
Printing a % in a format string
Printing a new line
next line starts here

 

Common Programming Error 28.2

Trying to print a literal percent character using % rather than %% in the format string might cause a difficult-to-detect logic error. When % appears in a format string, it must be followed by a conversion character in the string. The single percent could accidentally be followed by a legitimate conversion character, thus causing a logic error.