Problem You want to find text regardless of case. Solution Compile the Pattern passing in the flags argument Pattern.CASE_INSENSITIVE to indicate that matching should be case-independent ("fold" or ignore differences in case). If your code might run in different locales (see Chapter 15), add Pattern.UNICODE_CASE. Without these flags, the default is normal, case-sensitive matching behavior. This flag (and others) are passed to the Pattern.compile( ) method, as in: // CaseMatch.java Pattern reCaseInsens = Pattern.compile(pattern, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE); reCaseInsens.matches(input); // will match case-insensitively
This flag must be passed when you create the Pattern; as Pattern objects are immutable, they cannot be changed once constructed. The full source code for this example is online as CaseMatch.java. Pattern.compile( ) Flags Half a dozen flags can be passed as the second argument to Pattern.compile( ) . If more than one value is needed, they can be or'd together using the | bitwise or operator. In alphabetical order, the flags are:
- CANON_EQ
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Enables so-called "canonical equivalence," that is, characters are matched by their base character, so that the character e followed by the "combining character mark" for the acute accent ( ´ ) can be matched either by the composite character é or the letter e followed by the character mark for the accent (see Recipe 4.8).
- CASE_INSENSITIVE
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Turns on case-insensitive matching (see Recipe Recipe 4.7).
- COMMENTS
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Causes whitespace and comments (from # to end-of-line) to be ignored in the pattern.
- DOTALL
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Allows dot (.) to match any regular character or the newline, not just newline (see Recipe Recipe 4.9).
- MULTILINE
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Specifies multiline mode (see Recipe Recipe 4.9).
- UNICODE_CASE
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Enables Unicode-aware case folding (see Recipe 4.7).
- UNIX_LINES
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Makes \n the only valid "newline" sequence for MULTILINE mode (see Recipe 4.9).
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