Java Reference
In-Depth Information
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System.out.println( "Enter a sentence and press Enter" );
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String sentence = scanner.nextLine();
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// process user sentence
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String[] tokens = sentence.split( " " );
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System.out.printf( "Number of elements: %d%nThe tokens are:%n" ,
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tokens.length);
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for (String token : tokens)
System.out.println(token);
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}
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} // end class TokenTest
Enter a sentence and press Enter
This is a sentence with seven tokens
Number of elements: 7
The tokens are:
This
is
a
sentence
with
seven
tokens
Fig. 14.18 | StringTokenizer object used to tokenize strings. (Part 2 of 2.)
14.7 Regular Expressions, Class Pattern and Class
Matcher
A regular expression is a String that describes a search pattern for matching characters in
other String s. Such expressions are useful for validating input and ensuring that data is in
a particular format. For example, a ZIP code must consist of five digits, and a last name
must contain only letters, spaces, apostrophes and hyphens. One application of regular ex-
pressions is to facilitate the construction of a compiler. Often, a large and complex regular
expression is used to validate the syntax of a program . If the program code does not match
the regular expression, the compiler knows that there's a syntax error in the code.
Class String provides several methods for performing regular-expression operations,
the simplest of which is the matching operation. String method matches receives a
String that specifies the regular expression and matches the contents of the String object
on which it's called to the regular expression. The method returns a boolean indicating
whether the match succeeded.
A regular expression consists of literal characters and special symbols. Figure 14.19
specifies some predefined character classes that can be used with regular expressions. A
character class is an escape sequence that represents a group of characters. A digit is any
numeric character. A word character is any letter (uppercase or lowercase), any digit or the
underscore character. A white-space character is a space, a tab, a carriage return, a newline
or a form feed. Each character class matches a single character in the String we're
attempting to match with the regular expression.
 
 
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