Package org.apache.oro.text.awk
Class AwkCompiler
java.lang.Object
org.apache.oro.text.awk.AwkCompiler
- All Implemented Interfaces:
PatternCompiler
The AwkCompiler class is used to create compiled regular expressions
conforming to the Awk regular expression syntax. It generates
AwkPattern instances upon compilation to be used in conjunction
with an AwkMatcher instance. AwkMatcher finds true leftmost-longest
matches, so you must take care with how you formulate your regular
expression to avoid matching more than you really want.
The supported regular expression syntax is a superset of traditional AWK, but NOT to be confused with GNU AWK or other AWK variants. Additionally, this AWK implementation is DFA-based and only supports 8-bit ASCII. Consequently, these classes can perform very fast pattern matches in most cases.
This is the traditional Awk syntax that is supported:
- Alternatives separated by |
- Quantified atoms
- *
- Match 0 or more times.
- +
- Match 1 or more times.
- ?
- Match 0 or 1 times.
- Atoms
- regular expression within parentheses
- a . matches everything including newline
- a ^ is a null token matching the beginning of a string but has no relation to newlines (and is only valid at the beginning of a regex; this differs from traditional awk for the sake of efficiency in Java).
- a $ is a null token matching the end of a string but has no relation to newlines (and is only valid at the end of a regex; this differs from traditional awk for the sake of efficiency in Java).
- Character classes (e.g., [abcd]) and ranges (e.g. [a-z])
- Special backslashed characters work within a character class
- Special backslashed characters
- \b
- backspace
- \n
- newline
- \r
- carriage return
- \t
- tab
- \f
- formfeed
- \xnn
- hexadecimal representation of character
- \nn or \nnn
- octal representation of character
- Any other backslashed character matches itself
This is the extended syntax that is supported:
- Quantified atoms
- {n,m}
- Match at least n but not more than m times.
- {n,}
- Match at least n times.
- {n}
- Match exactly n times.
- Atoms
- Special backslashed characters
- \d
- digit [0-9]
- \D
- non-digit [^0-9]
- \w
- word character [0-9a-z_A-Z]
- \W
- a non-word character [^0-9a-z_A-Z]
- \s
- a whitespace character [ \t\n\r\f]
- \S
- a non-whitespace character [^ \t\n\r\f]
- \cD
- matches the corresponding control character
- \0
- matches null character
- Special backslashed characters
- Since:
- 1.0
- Version:
- 2.0.8
- See Also:
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
A mask passed as an option to thecompile
methods to indicate a compiled regular expression should be case insensitive.static final int
The default mask for thecompile
methods.static final int
A mask passed as an option to thecompile
methods to indicate a compiled regular expression should treat input as having multiple lines. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptioncompile
(char[] pattern) Same as calling compile(pattern, AwkCompiler.DEFAULT_MASK);compile
(char[] pattern, int options) Compiles an Awk regular expression into an AwkPattern instance that can be used by an AwkMatcher object to perform pattern matching.Same as calling compile(pattern, AwkCompiler.DEFAULT_MASK);Compiles an Awk regular expression into an AwkPattern instance that can be used by an AwkMatcher object to perform pattern matching.
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Field Details
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DEFAULT_MASK
public static final int DEFAULT_MASKThe default mask for thecompile
methods. It is equal to 0 and indicates no special options are active.- See Also:
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CASE_INSENSITIVE_MASK
public static final int CASE_INSENSITIVE_MASKA mask passed as an option to thecompile
methods to indicate a compiled regular expression should be case insensitive.- See Also:
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MULTILINE_MASK
public static final int MULTILINE_MASKA mask passed as an option to thecompile
methods to indicate a compiled regular expression should treat input as having multiple lines. This option affects the interpretation of the . metacharacters. When this mask is used, the . metacharacter will not match newlines. The default behavior is for . to match newlines.- See Also:
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Constructor Details
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AwkCompiler
public AwkCompiler()
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Method Details
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compile
Compiles an Awk regular expression into an AwkPattern instance that can be used by an AwkMatcher object to perform pattern matching.- Specified by:
compile
in interfacePatternCompiler
- Parameters:
pattern
- An Awk regular expression to compile.options
- A set of flags giving the compiler instructions on how to treat the regular expression. Currently the only meaningful flag is AwkCompiler.CASE_INSENSITIVE_MASK.- Returns:
- A Pattern instance constituting the compiled regular expression. This instance will always be an AwkPattern and can be reliably be casted to an AwkPattern.
- Throws:
MalformedPatternException
- If the compiled expression is not a valid Awk regular expression.
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compile
Compiles an Awk regular expression into an AwkPattern instance that can be used by an AwkMatcher object to perform pattern matching.- Specified by:
compile
in interfacePatternCompiler
- Parameters:
pattern
- An Awk regular expression to compile.options
- A set of flags giving the compiler instructions on how to treat the regular expression. Currently the only meaningful flag is AwkCompiler.CASE_INSENSITIVE_MASK.- Returns:
- A Pattern instance constituting the compiled regular expression. This instance will always be an AwkPattern and can be reliably be casted to an AwkPattern.
- Throws:
MalformedPatternException
- If the compiled expression is not a valid Awk regular expression.
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compile
Same as calling compile(pattern, AwkCompiler.DEFAULT_MASK);- Specified by:
compile
in interfacePatternCompiler
- Parameters:
pattern
- A regular expression to compile.- Returns:
- A Pattern instance constituting the compiled regular expression. This instance will always be an AwkPattern and can be reliably be casted to an AwkPattern.
- Throws:
MalformedPatternException
- If the compiled expression is not a valid Awk regular expression.
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compile
Same as calling compile(pattern, AwkCompiler.DEFAULT_MASK);- Specified by:
compile
in interfacePatternCompiler
- Parameters:
pattern
- A regular expression to compile.- Returns:
- A Pattern instance constituting the compiled regular expression. This instance will always be an AwkPattern and can be reliably be casted to an AwkPattern.
- Throws:
MalformedPatternException
- If the compiled expression is not a valid Awk regular expression.
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