Java Data and Operators

7.2. Lexical Ordering

The order in which the characters of a character set are arranged, their lexical order, is an important feature of the character set. It especially comes into play for such tasks as arranging strings in alphabetical order.

Although the actual integer values assigned to the individual characters by ASCII and UNICODE encoding seem somewhat arbitrary, the characters are, in fact, arranged in a particular order. For example, note that various sequences of digits, '0'...'9', and letters, 'a'...'z' and 'A'...'Z', are represented by sequences of integers (Table 5.11). This makes it possible to represent the lexical order of the characters in terms of the less than relationship among integers. The fact that 'a' comes before 'f' in alphabetical order is represented by the fact that 97 (the integer code for 'a') is less than 102 (the integer code for 'f'). Similarly, the digit '5' comes before the digit '9' in an alphabetical sequence because 53 (the integer code for '5') is less than 57 (the integer code for '9').

This ordering relationship extends throughout the character set. Thus, it is also the case that 'A' comes before 'a' in the lexical ordering because 65 (the integer code for 'A') is less than 97 (the integer code for 'a'). Similarly, the character '[' comes before '}' because its integer code (91) is less than 125, the integer code for '}'.