Pattern Matching - Revision history

Suhridk: /* Quantifiers */

2011-09-10T08:12:14Z

Quantifiers

2011-09-10T07:59:21Z

Metacharacters and Character Classes

2011-09-10T07:53:46Z

Metacharacters and Character Classes

2011-09-10T07:52:16Z

Metacharacters and Character Classes

2011-09-09T15:48:25Z

Tokenizing (Scanner)

2011-09-05T06:01:47Z

Tokenizing

2011-08-19T08:06:32Z

Tokenizing

2011-07-06T09:45:54Z

Metacharacters and Character Classes

2011-07-06T07:59:18Z

Quantifiers

2011-07-06T07:57:27Z

Quantifiers

@@ Line 239: / Line 239: @@
 * \d\d+ means a digit followed by zero or one more digit.
 * abc+ means a followed by b, followed by c one or more times.
-* (abc)+ means the group "abc" one or more times.
+* '''(abc)+ means the group "abc" one or more times.'''
-* [abc]+ would mean a OR b OR c one or more times.
+* '''[abc]+ would mean a OR b OR c one or more times.'''
 === Greedy Quantifiers ===

@@ Line 82: / Line 82: @@
 ** \d - Matches a digit
 ** \D - Matches a non-digit equivalent to [^\d]
-** \s - Matches a whitespace char
+** \s - Matches a whitespace char ([ \t\n\x0B\f\r])
 ** \S - Matches a non-whitespace char
 ** \w - Matches a word char (letters/digits or _)

@@ Line 73: / Line 73: @@
 ** [a-fA-F] - a to f OR A to F
 ** [a-d[m-p]] - a through d OR m through p
-** [^aeiouAEIOUS] - no vowels
+** [a-z&&[def]] - d, e, or f (intersection)
 * Predefined character classes:

@@ Line 71: / Line 71: @@
 ** [abc] - Only a's or b's or c's
 ** [a-f] - Search for a,b,c,d,e,f chars
-** [a-fA-F] - small and caps
+** [a-fA-F] - a to f OR A to F
 ** [^aeiouAEIOUS] - no vowels

← Older revision		Revision as of 15:48, 9 September 2011
Line 332:		Line 332:

	* Another example, where a regex is being used as a delimiter to the scanner:		* Another example, where a regex is being used as a delimiter to the scanner:
		+	* In the hasNext(Pattern) method attempts to match the '''complete''' token to the Pattern ! Works like Mather's matches() method.

	<syntaxhighlight lang="java5">		<syntaxhighlight lang="java5">

@@ Line 281: / Line 281: @@
 </syntaxhighlight>
-== Tokenizing ==
+== Tokenizing (Scanner) ==
 * Tokenizing for small pieces of data can be done by the String.split() method.
@@ Line 370: / Line 370: @@
 </syntaxhighlight>
 [[Category:OCPJP]]

← Older revision		Revision as of 08:06, 19 August 2011
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	}		}

		+	</syntaxhighlight>
		+
		+
		+	* Scanner '''will throw an InputMismatchException''' when it can't convert the next token of the input into the desired type.
		+	* Example: when the scanner reaches the token abc, it will throw an exception.
		+
		+	<syntaxhighlight lang="java5">
		+
		+	Scanner s = new Scanner("123 abc");
		+	while(s.hasNext()) {
		+	int i = s.nextInt();
		+	}
	</syntaxhighlight>		</syntaxhighlight>

@@ Line 177: / Line 177: @@
 ,6: a
 ,6:
 Target: banana
@@ Line 186: / Line 185: @@
 ,6: a
-Target: banana
+Target: banaana
 Pattern: a*
 Match:
 Target: banana
-Pattern: a*
+Pattern: a?
 Match:
 Target: banana
-Pattern: a*
+Pattern: a+
 Match:

@@ Line 148: / Line 148: @@
 * ? - Zero or one occurrence.
 * + - One or more occurrence.
 * Consider the pattern a? - it means zero or one a's to be searched for.
 * In the string banana, the engine will match all the characters in the target, since it is searching for zero or one a's.
 * '''Now, where the char is not an a, the empty string is returned in the match.''' - the regex engine inserts empty strings in the input to match the pattern a?.