STRINGS - Introduction to Java Programming - page 350

public static int hexCharToDecimal(char ch) {

hex char to decimal

27
28 if (ch >= 'A' && ch <= 'F' ) to uppercase

29 return 10 + ch - 'A' ;

30 else // ch is '0', '1', ..., or '9'

31 return ch - '0' ;

32 }
33 }

AB8C

Enter a hex number:
The decimal value for hex number AB8C is 43916

af71

Enter a hex number:
The decimal value for hex number af71 is 44913

The program reads a string from the console (line 11), and invokes the hexToDecimal method
to convert a hex string to decimal number (line 14). The characters can be in either lowercase
or uppercase. They are converted to uppercase before invoking the hexToDecimal method.
The hexToDecimal method is defined in lines 17-25 to return an integer. The length of
the string is determined by invoking hex.length() in line 19.
The hexCharToDecimal method is defined in lines 27-32 to return a decimal value for a
hex character. The character can be in either lowercase or uppercase. Recall that to subtract
two characters is to subtract their Unicodes. For example, '5' - '0' is 5 .

9.5 The Character Class
You can create an object for a character using the Character class. A Character
object contains a character value.

Key
Point

Many methods in the Java API require an object argument. To enable the primitive data values
to be treated as objects, Java provides a class for every primitive data type. These classes are
Character , Boolean , Byte , Short , Integer , Long , Float , and Double for char ,
boolean , byte , short , int , long , float , and double , respectively. These classes are
called wrapper classes because each wraps or encapsulates a primitive type value in an object.
All these classes are in the java.lang package, and they contain useful methods for
processing primitive values. This section introduces the Character class. The other wrapper
classes will be introduced in Chapter 10, Thinking in Objects.
The Character class has a constructor and several methods for determining a character's
category (uppercase, lowercase, digit, and so on) and for converting characters from upper-
case to lowercase, and vice versa, as shown in Figure 9.10.
You can create a Character object from a char value. For example, the following state-
ment creates a Character object for the character a .

wrapper class

Character character = new Character( 'a' );

The charValue method returns the character value wrapped in the Character object. The
compareTo method compares this character with another character and returns an integer
that is the difference between the Unicode of this character and the Unicode of the other char-
acter. The equals method returns true if and only if the two characters are the same. For
example, suppose charObject is new Character('b') :

returns 1
charObject.compareTo(new Character('b')) returns 0
charObject.compareTo(new Character('c'))

charObject.compareTo(new Character('a'))

returns -1