RE (Codename One API)

java.lang.Object
- com.codename1.util.regex.RE

public class RE
extends Object

RE is an efficient, lightweight regular expression evaluator/matcher class. Regular expressions are pattern descriptions which enable sophisticated matching of strings. In addition to being able to match a string against a pattern, you can also extract parts of the match. This is especially useful in text parsing! Details on the syntax of regular expression patterns are given below.

To compile a regular expression (RE), you can simply construct an RE matcher object from the string specification of the pattern, like this:

  RE r = new RE("a*b");

Once you have done this, you can call either of the RE.match methods to perform matching on a String. For example:

  boolean matched = r.match("aaaab");

will cause the boolean matched to be set to true because the pattern "a*b" matches the string "aaaab".

If you were interested in the number of a's which matched the first part of our example expression, you could change the expression to "(a*)b". Then when you compiled the expression and matched it against something like "xaaaab", you would get results like this:

  RE r = new RE("(a*)b");                  // Compile expression
  boolean matched = r.match("xaaaab");     // Match against "xaaaab"

  String wholeExpr = r.getParen(0);        // wholeExpr will be 'aaaab'
  String insideParens = r.getParen(1);     // insideParens will be 'aaaa'

  int startWholeExpr = r.getParenStart(0); // startWholeExpr will be index 1
  int endWholeExpr = r.getParenEnd(0);     // endWholeExpr will be index 6
  int lenWholeExpr = r.getParenLength(0);  // lenWholeExpr will be 5

  int startInside = r.getParenStart(1);    // startInside will be index 1
  int endInside = r.getParenEnd(1);        // endInside will be index 5
  int lenInside = r.getParenLength(1);     // lenInside will be 4

You can also refer to the contents of a parenthesized expression within a regular expression itself. This is called a 'backreference'. The first backreference in a regular expression is denoted by \1, the second by \2 and so on. So the expression:

  ([0-9]+)=\1

will match any string of the form n=n (like 0=0 or 2=2).

The full regular expression syntax accepted by RE is described here:


  Characters

    unicodeChar   Matches any identical unicode character
    \                    Used to quote a meta-character (like '*')
    \\                   Matches a single '\' character
    \0nnn                Matches a given octal character
    \xhh                 Matches a given 8-bit hexadecimal character
    \\uhhhh              Matches a given 16-bit hexadecimal character
    \t                   Matches an ASCII tab character
    \n                   Matches an ASCII newline character
    \r                   Matches an ASCII return character
    \f                   Matches an ASCII form feed character


  Character Classes

    [abc]                Simple character class
    [a-zA-Z]             Character class with ranges
    [^abc]               Negated character class

NOTE: Incomplete ranges will be interpreted as "starts from zero" or "ends with last character".
I.e. [-a] is the same as [\\u0000-a], and [a-] is the same as [a-\\uFFFF], [-] means "all characters".


  Standard POSIX Character Classes

    [:alnum:]            Alphanumeric characters.
    [:alpha:]            Alphabetic characters.
    [:blank:]            Space and tab characters.
    [:cntrl:]            Control characters.
    [:digit:]            Numeric characters.
    [:graph:]            Characters that are printable and are also visible.
                         (A space is printable, but not visible, while an
                         `a' is both.)
    [:lower:]            Lower-case alphabetic characters.
    [:print:]            Printable characters (characters that are not
                         control characters.)
    [:punct:]            Punctuation characters (characters that are not letter,
                         digits, control characters, or space characters).
    [:space:]            Space characters (such as space, tab, and formfeed,
                         to name a few).
    [:upper:]            Upper-case alphabetic characters.
    [:xdigit:]           Characters that are hexadecimal digits.


  Non-standard POSIX-style Character Classes

    [:javastart:]        Start of a Java identifier
    [:javapart:]         Part of a Java identifier


  Predefined Classes

    .         Matches any character other than newline
    \w        Matches a "word" character (alphanumeric plus "_")
    \W        Matches a non-word character
    \s        Matches a whitespace character
    \S        Matches a non-whitespace character
    \d        Matches a digit character
    \D        Matches a non-digit character


  Boundary Matchers

    ^         Matches only at the beginning of a line
    $         Matches only at the end of a line
    \b        Matches only at a word boundary
    \B        Matches only at a non-word boundary


  Greedy Closures

    A*        Matches A 0 or more times (greedy)
    A+        Matches A 1 or more times (greedy)
    A?        Matches A 1 or 0 times (greedy)
    A{n}      Matches A exactly n times (greedy)
    A{n,}     Matches A at least n times (greedy)
    A{n,m}    Matches A at least n but not more than m times (greedy)


  Reluctant Closures

    A*?       Matches A 0 or more times (reluctant)
    A+?       Matches A 1 or more times (reluctant)
    A??       Matches A 0 or 1 times (reluctant)


  Logical Operators

    AB        Matches A followed by B
    A|B       Matches either A or B
    (A)       Used for subexpression grouping
   (?:A)      Used for subexpression clustering (just like grouping but
              no backrefs)


  Backreferences

    \1    Backreference to 1st parenthesized subexpression
    \2    Backreference to 2nd parenthesized subexpression
    \3    Backreference to 3rd parenthesized subexpression
    \4    Backreference to 4th parenthesized subexpression
    \5    Backreference to 5th parenthesized subexpression
    \6    Backreference to 6th parenthesized subexpression
    \7    Backreference to 7th parenthesized subexpression
    \8    Backreference to 8th parenthesized subexpression
    \9    Backreference to 9th parenthesized subexpression

All closure operators (+, *, ?, {m,n}) are greedy by default, meaning that they match as many elements of the string as possible without causing the overall match to fail. If you want a closure to be reluctant (non-greedy), you can simply follow it with a '?'. A reluctant closure will match as few elements of the string as possible when finding matches. {m,n} closures don't currently support reluctancy.

Line terminators
A line terminator is a one- or two-character sequence that marks the end of a line of the input character sequence. The following are recognized as line terminators:

A newline (line feed) character ('\n'),
A carriage-return character followed immediately by a newline character ("\r\n"),
A standalone carriage-return character ('\r'),
A next-line character (''),
A line-separator character (' '), or
A paragraph-separator character (' ).

RE runs programs compiled by the RECompiler class. But the RE matcher class does not include the actual regular expression compiler for reasons of efficiency. You can construct a single RECompiler object and re-use it to compile each expression. Similarly, you can change the program run by a given matcher object at any time. However, RE and RECompiler are not threadsafe (for efficiency reasons, and because requiring thread safety in this class is deemed to be a rare requirement), so you will need to construct a separate compiler or matcher object for each thread (unless you do thread synchronization yourself). Once expression compiled into the REProgram object, REProgram can be safely shared across multiple threads and RE objects.

ISSUES:

com.weusours.util.re is not currently compatible with all standard POSIX regcomp flags

com.weusours.util.re does not support POSIX equivalence classes ([=foo=] syntax) (I18N/locale issue)

com.weusours.util.re does not support nested POSIX character classes (definitely should, but not completely trivial)

com.weusours.util.re Does not support POSIX character collation concepts ([.foo.] syntax) (I18N/locale issue)

Should there be different matching styles (simple, POSIX, Perl etc?)

Should RE support character iterators (for backwards RE matching!)?

Should RE support reluctant {m,n} closures (does anyone care)?

Not *all* possibilities are considered for greediness when backreferences are involved (as POSIX suggests should be the case). The POSIX RE "(ac*)c*d[ac]*\1", when matched against "acdacaa" should yield a match of acdacaa where \1 is "a". This is not the case in this RE package, and actually Perl doesn't go to this extent either! Until someone actually complains about this, I'm not sure it's worth "fixing". If it ever is fixed, test #137 in RETest.txt should be updated.

See Also:: RECompiler

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`MATCH_CASEINDEPENDENT` Flag to indicate that matching should be case-independent (folded)
`static int`	`MATCH_MULTILINE` Newlines should match as BOL/EOL (^ and $)
`static int`	`MATCH_NORMAL` Specifies normal, case-sensitive matching behaviour.
`static int`	`MATCH_SINGLELINE` Consider all input a single body of text - newlines are matched by .
`static int`	`REPLACE_ALL` Flag bit that indicates that subst should replace all occurrences of this regular expression.
`static int`	`REPLACE_BACKREFERENCES` Flag bit that indicates that subst should replace backreferences
`static int`	`REPLACE_FIRSTONLY` Flag bit that indicates that subst should only replace the first occurrence of this regular expression.

Constructor Summary

Constructors
Constructor and Description
`RE()` Constructs a regular expression matcher with no initial program.
`RE(REProgram program)` Construct a matcher for a pre-compiled regular expression from program (bytecode) data.
`RE(REProgram program, int matchFlags)` Construct a matcher for a pre-compiled regular expression from program (bytecode) data.
`RE(String pattern)` Constructs a regular expression matcher from a String by compiling it using a new instance of RECompiler.
`RE(String pattern, int matchFlags)` Constructs a regular expression matcher from a String by compiling it using a new instance of RECompiler.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`int`	`getMatchFlags()` Returns the current match behaviour flags.
`String`	`getParen(int which)` Gets the contents of a parenthesized subexpression after a successful match.
`int`	`getParenCount()` Returns the number of parenthesized subexpressions available after a successful match.
`int`	`getParenEnd(int which)` Returns the end index of a given paren level.
`int`	`getParenLength(int which)` Returns the length of a given paren level.
`int`	`getParenStart(int which)` Returns the start index of a given paren level.
`REProgram`	`getProgram()` Returns the current regular expression program in use by this matcher object.
`String[]`	`grep(Object[] search)` Returns an array of Strings, whose toString representation matches a regular expression.
`protected void`	`internalError(String s)` Throws an Error representing an internal error condition probably resulting from a bug in the regular expression compiler (or possibly data corruption).
`boolean`	`match(CharacterIterator search, int i)` Matches the current regular expression program against a character array, starting at a given index.
`boolean`	`match(String search)` Matches the current regular expression program against a String.
`boolean`	`match(String search, int i)` Matches the current regular expression program against a character array, starting at a given index.
`protected boolean`	`matchAt(int i)` Match the current regular expression program against the current input string, starting at index i of the input string.
`protected int`	`matchNodes(int firstNode, int lastNode, int idxStart)` Try to match a string against a subset of nodes in the program
`void`	`setMatchFlags(int matchFlags)` Sets match behaviour flags which alter the way RE does matching.
`protected void`	`setParenEnd(int which, int i)` Sets the end of a paren level
`protected void`	`setParenStart(int which, int i)` Sets the start of a paren level
`void`	`setProgram(REProgram program)` Sets the current regular expression program used by this matcher object.
`static String`	`simplePatternToFullRegularExpression(String pattern)` Converts a 'simplified' regular expression to a full regular expression
`String[]`	`split(String s)` Splits a string into an array of strings on regular expression boundaries.
`String`	`subst(String substituteIn, String substitution)` Substitutes a string for this regular expression in another string.
`String`	`subst(String substituteIn, String substitution, int flags)` Substitutes a string for this regular expression in another string.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - MATCH_NORMAL
```
public static final int MATCH_NORMAL
```
    Specifies normal, case-sensitive matching behaviour.
    
    See Also:
    
    Constant Field Values
  - MATCH_CASEINDEPENDENT
```
public static final int MATCH_CASEINDEPENDENT
```
    Flag to indicate that matching should be case-independent (folded)
    
    See Also:
    
    Constant Field Values
  - MATCH_MULTILINE
```
public static final int MATCH_MULTILINE
```
    Newlines should match as BOL/EOL (^ and $)
    
    See Also:
    
    Constant Field Values
  - MATCH_SINGLELINE
```
public static final int MATCH_SINGLELINE
```
    Consider all input a single body of text - newlines are matched by .
    
    See Also:
    
    Constant Field Values
  - REPLACE_ALL
```
public static final int REPLACE_ALL
```
    Flag bit that indicates that subst should replace all occurrences of this regular expression.
    
    See Also:
    
    Constant Field Values
  - REPLACE_FIRSTONLY
```
public static final int REPLACE_FIRSTONLY
```
    Flag bit that indicates that subst should only replace the first occurrence of this regular expression.
    
    See Also:
    
    Constant Field Values
  - REPLACE_BACKREFERENCES
```
public static final int REPLACE_BACKREFERENCES
```
    Flag bit that indicates that subst should replace backreferences
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - RE
```
public RE(String pattern)
   throws RESyntaxException
```
    Constructs a regular expression matcher from a String by compiling it using a new instance of RECompiler. If you will be compiling many expressions, you may prefer to use a single RECompiler object instead.
    
    Parameters:
    
    pattern - The regular expression pattern to compile.
    
    Throws:
    
    RESyntaxException - Thrown if the regular expression has invalid syntax.
    
    See Also:
    
    RECompiler
  - RE
```
public RE(String pattern,
          int matchFlags)
   throws RESyntaxException
```
    Constructs a regular expression matcher from a String by compiling it using a new instance of RECompiler. If you will be compiling many expressions, you may prefer to use a single RECompiler object instead.
    
    Parameters:
    
    pattern - The regular expression pattern to compile.
    
    matchFlags - The matching style
    
    Throws:
    
    RESyntaxException - Thrown if the regular expression has invalid syntax.
    
    See Also:
    
    RECompiler
  - RE
```
public RE(REProgram program,
          int matchFlags)
```
    Construct a matcher for a pre-compiled regular expression from program (bytecode) data. Permits special flags to be passed in to modify matching behaviour.
    Parameters:
    
    program - Compiled regular expression program (see RECompiler)
    matchFlags - One or more of the RE match behaviour flags (RE.MATCH_*):
    MATCH_NORMAL // Normal (case-sensitive) matching MATCH_CASEINDEPENDENT // Case folded comparisons MATCH_MULTILINE // Newline matches as BOL/EOL
    See Also:
    
    RECompiler, REProgram
  - RE
```
public RE(REProgram program)
```
    Construct a matcher for a pre-compiled regular expression from program (bytecode) data.
    
    Parameters:
    
    program - Compiled regular expression program
    
    See Also:
    
    RECompiler
  - RE
```
public RE()
```
    Constructs a regular expression matcher with no initial program. This is likely to be an uncommon practice, but is still supported.
- Method Detail
  - simplePatternToFullRegularExpression
```
public static String simplePatternToFullRegularExpression(String pattern)
```
    Converts a 'simplified' regular expression to a full regular expression
    
    Parameters:
    
    pattern - The pattern to convert
    
    Returns:
    
    The full regular expression
  - setMatchFlags
```
public void setMatchFlags(int matchFlags)
```
    Sets match behaviour flags which alter the way RE does matching.
    Parameters:
    matchFlags - One or more of the RE match behaviour flags (RE.MATCH_*):
    MATCH_NORMAL // Normal (case-sensitive) matching MATCH_CASEINDEPENDENT // Case folded comparisons MATCH_MULTILINE // Newline matches as BOL/EOL
  - getMatchFlags
```
public int getMatchFlags()
```
    Returns the current match behaviour flags.
    Returns:
    Current match behaviour flags (RE.MATCH_*).
    MATCH_NORMAL // Normal (case-sensitive) matching MATCH_CASEINDEPENDENT // Case folded comparisons MATCH_MULTILINE // Newline matches as BOL/EOL
    See Also:
    
    setMatchFlags(int)
  - setProgram
```
public void setProgram(REProgram program)
```
    Sets the current regular expression program used by this matcher object.
    
    Parameters:
    
    program - Regular expression program compiled by RECompiler.
    
    See Also:
    
    RECompiler, REProgram
  - getProgram
```
public REProgram getProgram()
```
    Returns the current regular expression program in use by this matcher object.
    
    Returns:
    
    Regular expression program
    
    See Also:
    
    setProgram(com.codename1.util.regex.REProgram)
  - getParenCount
```
public int getParenCount()
```
    Returns the number of parenthesized subexpressions available after a successful match.
    
    Returns:
    
    Number of available parenthesized subexpressions
  - getParen
```
public String getParen(int which)
```
    Gets the contents of a parenthesized subexpression after a successful match.
    
    Parameters:
    
    which - Nesting level of subexpression
    
    Returns:
    
    String
  - getParenStart
```
public final int getParenStart(int which)
```
    Returns the start index of a given paren level.
    
    Parameters:
    
    which - Nesting level of subexpression
    
    Returns:
    
    String index
  - getParenEnd
```
public final int getParenEnd(int which)
```
    Returns the end index of a given paren level.
    
    Parameters:
    
    which - Nesting level of subexpression
    
    Returns:
    
    String index
  - getParenLength
```
public final int getParenLength(int which)
```
    Returns the length of a given paren level.
    
    Parameters:
    
    which - Nesting level of subexpression
    
    Returns:
    
    Number of characters in the parenthesized subexpression
  - setParenStart
```
protected final void setParenStart(int which,
                                   int i)
```
    Sets the start of a paren level
    
    Parameters:
    
    which - Which paren level
    
    i - Index in input array
  - setParenEnd
```
protected final void setParenEnd(int which,
                                 int i)
```
    Sets the end of a paren level
    
    Parameters:
    
    which - Which paren level
    
    i - Index in input array
  - internalError
```
protected void internalError(String s)
                      throws Error
```
    Throws an Error representing an internal error condition probably resulting from a bug in the regular expression compiler (or possibly data corruption). In practice, this should be very rare.
    
    Parameters:
    
    s - Error description
    
    Throws:
    
    Error
  - matchNodes
```
protected int matchNodes(int firstNode,
                         int lastNode,
                         int idxStart)
```
    Try to match a string against a subset of nodes in the program
    
    Parameters:
    
    firstNode - Node to start at in program
    
    lastNode - Last valid node (used for matching a subexpression without matching the rest of the program as well).
    
    idxStart - Starting position in character array
    
    Returns:
    
    Final input array index if match succeeded. -1 if not.
  - matchAt
```
protected boolean matchAt(int i)
```
    Match the current regular expression program against the current input string, starting at index i of the input string. This method is only meant for internal use.
    
    Parameters:
    
    i - The input string index to start matching at
    
    Returns:
    
    True if the input matched the expression
  - match
```
public boolean match(String search,
                     int i)
```
    Matches the current regular expression program against a character array, starting at a given index.
    
    Parameters:
    
    search - String to match against
    
    i - Index to start searching at
    
    Returns:
    
    True if string matched
  - match
```
public boolean match(CharacterIterator search,
                     int i)
```
    Matches the current regular expression program against a character array, starting at a given index.
    
    Parameters:
    
    search - String to match against
    
    i - Index to start searching at
    
    Returns:
    
    True if string matched
  - match
```
public boolean match(String search)
```
    Matches the current regular expression program against a String.
    
    Parameters:
    
    search - String to match against
    
    Returns:
    
    True if string matched
  - split
```
public String[] split(String s)
```
    Splits a string into an array of strings on regular expression boundaries. This function works the same way as the Perl function of the same name. Given a regular expression of "[ab]+" and a string to split of "xyzzyababbayyzabbbab123", the result would be the array of Strings "[xyzzy, yyz, 123]".
    Please note that the first string in the resulting array may be an empty string. This happens when the very first character of input string is matched by the pattern.
    
    Parameters:
    
    s - String to split on this regular exression
    
    Returns:
    
    Array of strings
  - subst
```
public String subst(String substituteIn,
                    String substitution)
```
    Substitutes a string for this regular expression in another string. This method works like the Perl function of the same name. Given a regular expression of "a*b", a String to substituteIn of "aaaabfooaaabgarplyaaabwackyb" and the substitution String "-", the resulting String returned by subst would be "-foo-garply-wacky-".
    
    Parameters:
    
    substituteIn - String to substitute within
    
    substitution - String to substitute for all matches of this regular expression.
    
    Returns:
    
    The string substituteIn with zero or more occurrences of the current regular expression replaced with the substitution String (if this regular expression object doesn't match at any position, the original String is returned unchanged).
  - subst
```
public String subst(String substituteIn,
                    String substitution,
                    int flags)
```
    Substitutes a string for this regular expression in another string. This method works like the Perl function of the same name. Given a regular expression of "a*b", a String to substituteIn of "aaaabfooaaabgarplyaaabwackyb" and the substitution String "-", the resulting String returned by subst would be "-foo-garply-wacky-".
    It is also possible to reference the contents of a parenthesized expression with $0, $1, ... $9. A regular expression of "http://[\\.\\w\\-\\?/~_@&=%]+", a String to substituteIn of "visit us: http://www.apache.org!" and the substitution String "<a href=\"$0\">$0</a>", the resulting String returned by subst would be "visit us: <a href=\"http://www.apache.org\">http://www.apache.org</a>!".
    Note: $0 represents the whole match.
    
    Parameters:
    
    substituteIn - String to substitute within
    
    substitution - String to substitute for matches of this regular expression
    
    flags - One or more bitwise flags from REPLACE_*. If the REPLACE_FIRSTONLY flag bit is set, only the first occurrence of this regular expression is replaced. If the bit is not set (REPLACE_ALL), all occurrences of this pattern will be replaced. If the flag REPLACE_BACKREFERENCES is set, all backreferences will be processed.
    
    Returns:
    
    The string substituteIn with zero or more occurrences of the current regular expression replaced with the substitution String (if this regular expression object doesn't match at any position, the original String is returned unchanged).
  - grep
```
public String[] grep(Object[] search)
```
    Returns an array of Strings, whose toString representation matches a regular expression. This method works like the Perl function of the same name. Given a regular expression of "a*b" and an array of String objects of [foo, aab, zzz, aaaab], the array of Strings returned by grep would be [aab, aaaab].
    
    Parameters:
    
    search - Array of Objects to search
    
    Returns:
    
    Array of Strings whose toString() value matches this regular expression.

Class RE

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MATCH_NORMAL

MATCH_CASEINDEPENDENT

MATCH_MULTILINE

MATCH_SINGLELINE

REPLACE_ALL

REPLACE_FIRSTONLY

REPLACE_BACKREFERENCES

Constructor Detail

RE

RE

RE

RE

RE

Method Detail

simplePatternToFullRegularExpression

setMatchFlags

getMatchFlags

setProgram

getProgram

getParenCount

getParen

getParenStart

getParenEnd

getParenLength

setParenStart

setParenEnd

internalError

matchNodes

matchAt

match

match

match

split

subst

subst

grep