org.graalvm.shadowed.com.ibm.icu.text

Class SearchIterator

java.lang.Object

org.graalvm.shadowed.com.ibm.icu.text.SearchIterator

Direct Known Subclasses:

StringSearch

public abstract class SearchIterator
extends Object

SearchIterator is an abstract base class that provides methods to search for a pattern within a text string. Instances of SearchIterator maintain a current position and scan over the target text, returning the indices the pattern is matched and the length of each match.

SearchIterator defines a protocol for text searching. Subclasses provide concrete implementations of various search algorithms. For example, StringSearch implements language-sensitive pattern matching based on the comparison rules defined in a RuleBasedCollator object.

Other options for searching include using a BreakIterator to restrict the points at which matches are detected.

SearchIterator provides an API that is similar to that of other text iteration classes such as BreakIterator. Using this class, it is easy to scan through text looking for all occurrences of a given pattern. The following example uses a StringSearch object to find all instances of "fox" in the target string. Any other subclass of SearchIterator can be used in an identical manner.

 String target = "The quick brown fox jumped over the lazy fox";
 String pattern = "fox";
 SearchIterator iter = new StringSearch(pattern, target);
 for (int pos = iter.first(); pos != SearchIterator.DONE;
         pos = iter.next()) {
     System.out.println("Found match at " + pos +
             ", length is " + iter.getMatchLength());
 }
 

See Also:

BreakIterator, RuleBasedCollator

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SearchIterator.ElementComparisonType Option to control how collation elements are compared.

Field Summary

Fields

Modifier and Type	Field and Description
protected BreakIterator	breakIterator The BreakIterator to define the boundaries of a logical match.
static int	DONE DONE is returned by previous() and next() after all valid matches have been returned, and by first() and last() if there are no matches at all.
protected int	matchLength Length of the most current match in target text.
protected CharacterIterator	targetText Target text for searching.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SearchIterator(CharacterIterator target, BreakIterator breaker) Protected constructor for use by subclasses.

Method Summary

Modifier and Type	Method and Description
int	first() Returns the first index at which the string text matches the search pattern.
int	following(int position) Returns the first index equal or greater than position at which the string text matches the search pattern.
BreakIterator	getBreakIterator() Returns the BreakIterator that is used to restrict the indexes at which matches are detected.
SearchIterator.ElementComparisonType	getElementComparisonType() Returns the collation element comparison type.
abstract int	getIndex() Return the current index in the text being searched.
String	getMatchedText() Returns the text that was matched by the most recent call to SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), or SearchIterator.last().
int	getMatchLength() Returns the length of text in the string which matches the search pattern.
int	getMatchStart() Returns the index to the match in the text string that was searched.
CharacterIterator	getTarget() Return the string text to be searched.
protected abstract int	handleNext(int start) Abstract method which subclasses override to provide the mechanism for finding the next match in the target text.
protected abstract int	handlePrevious(int startAt) Abstract method which subclasses override to provide the mechanism for finding the previous match in the target text.
boolean	isOverlapping() Return true if the overlapping property has been set.
int	last() Returns the last index in the target text at which it matches the search pattern.
int	next() Returns the index of the next point at which the text matches the search pattern, starting from the current position The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found.
int	preceding(int position) Returns the first index less than position at which the string text matches the search pattern.
int	previous() Returns the index of the previous point at which the string text matches the search pattern, starting at the current position.
void	reset() Resets the iteration.
void	setBreakIterator(BreakIterator breakiter) Set the BreakIterator that will be used to restrict the points at which matches are detected.
void	setElementComparisonType(SearchIterator.ElementComparisonType type) Sets the collation element comparison type.
void	setIndex(int position) Sets the position in the target text at which the next search will start.
protected void	setMatchLength(int length) Sets the length of the most recent match in the target text.
void	setOverlapping(boolean allowOverlap) Determines whether overlapping matches are returned.
void	setTarget(CharacterIterator text) Set the target text to be searched.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

breakIterator

protected BreakIterator breakIterator

The BreakIterator to define the boundaries of a logical match. This value can be a null. See class documentation for more information.

See Also:

SearchIterator.setBreakIterator(BreakIterator), SearchIterator.getBreakIterator(), BreakIterator

targetText

protected CharacterIterator targetText

Target text for searching.

See Also:

SearchIterator.setTarget(CharacterIterator), SearchIterator.getTarget()

matchLength

protected int matchLength

Length of the most current match in target text. Value 0 is the default value.

See Also:

SearchIterator.setMatchLength(int), SearchIterator.getMatchLength()

DONE

public static final int DONE

DONE is returned by previous() and next() after all valid matches have been returned, and by first() and last() if there are no matches at all.

See Also:

SearchIterator.previous(), SearchIterator.next(), Constant Field Values

Constructor Detail

SearchIterator

protected SearchIterator(CharacterIterator target,
                         BreakIterator breaker)

Protected constructor for use by subclasses. Initializes the iterator with the argument target text for searching and sets the BreakIterator. See class documentation for more details on the use of the target text and BreakIterator.

Parameters:

target - The target text to be searched.

breaker - A BreakIterator that is used to determine the boundaries of a logical match. This argument can be null.

Throws:

IllegalArgumentException - thrown when argument target is null, or of length 0

See Also:

BreakIterator

Method Detail

setIndex

public void setIndex(int position)

Sets the position in the target text at which the next search will start. This method clears any previous match.

Parameters:

position - position from which to start the next search

Throws:

IndexOutOfBoundsException - thrown if argument position is out of the target text range.

See Also:

SearchIterator.getIndex()

setOverlapping

public void setOverlapping(boolean allowOverlap)

Determines whether overlapping matches are returned. See the class documentation for more information about overlapping matches.

The default setting of this property is false

Parameters:

allowOverlap - flag indicator if overlapping matches are allowed

See Also:

SearchIterator.isOverlapping()

setBreakIterator

public void setBreakIterator(BreakIterator breakiter)

Set the BreakIterator that will be used to restrict the points at which matches are detected.

Parameters:

breakiter - A BreakIterator that will be used to restrict the points at which matches are detected. If a match is found, but the match's start or end index is not a boundary as determined by the BreakIterator, the match will be rejected and another will be searched for. If this parameter is null, no break detection is attempted.

See Also:

BreakIterator

setTarget

public void setTarget(CharacterIterator text)

Set the target text to be searched. Text iteration will then begin at the start of the text string. This method is useful if you want to reuse an iterator to search within a different body of text.

Parameters:

text - new text iterator to look for match,

Throws:

IllegalArgumentException - thrown when text is null or has 0 length

See Also:

SearchIterator.getTarget()

getMatchStart

public int getMatchStart()

Returns the index to the match in the text string that was searched. This call returns a valid result only after a successful call to SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), or SearchIterator.last(). Just after construction, or after a searching method returns SearchIterator.DONE, this method will return SearchIterator.DONE.

Use SearchIterator.getMatchLength() to get the matched string length.

Returns:

index of a substring within the text string that is being searched.

See Also:

SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), SearchIterator.last()

getIndex

public abstract int getIndex()

Return the current index in the text being searched. If the iteration has gone past the end of the text (or past the beginning for a backwards search), SearchIterator.DONE is returned.

Returns:

current index in the text being searched.

getMatchLength

public int getMatchLength()

Returns the length of text in the string which matches the search pattern. This call returns a valid result only after a successful call to SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), or SearchIterator.last(). Just after construction, or after a searching method returns SearchIterator.DONE, this method will return 0.

Returns:

The length of the match in the target text, or 0 if there is no match currently.

See Also:

SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), SearchIterator.last()

getBreakIterator

public BreakIterator getBreakIterator()

Returns the BreakIterator that is used to restrict the indexes at which matches are detected. This will be the same object that was passed to the constructor or to SearchIterator.setBreakIterator(org.graalvm.shadowed.com.ibm.icu.text.BreakIterator). If the BreakIterator has not been set, null will be returned. See SearchIterator.setBreakIterator(org.graalvm.shadowed.com.ibm.icu.text.BreakIterator) for more information.

Returns:

the BreakIterator set to restrict logic matches

See Also:

SearchIterator.setBreakIterator(org.graalvm.shadowed.com.ibm.icu.text.BreakIterator), BreakIterator

getTarget

public CharacterIterator getTarget()

Return the string text to be searched.

Returns:

text string to be searched.

getMatchedText

public String getMatchedText()

Returns the text that was matched by the most recent call to SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), or SearchIterator.last(). If the iterator is not pointing at a valid match (e.g. just after construction or after SearchIterator.DONE has been returned, returns an empty string.

Returns:

the substring in the target test of the most recent match, or null if there is no match currently.

See Also:

SearchIterator.first(), SearchIterator.next(), SearchIterator.previous(), SearchIterator.last()

next

public int next()

Returns the index of the next point at which the text matches the search pattern, starting from the current position The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to a position after the end of the text string.

Returns:

The index of the next match after the current position, or SearchIterator.DONE if there are no more matches.

See Also:

SearchIterator.getIndex()

previous

public int previous()

Returns the index of the previous point at which the string text matches the search pattern, starting at the current position. The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to the index SearchIterator.DONE.

Returns:

The index of the previous match before the current position, or SearchIterator.DONE if there are no more matches.

See Also:

SearchIterator.getIndex()

isOverlapping

public boolean isOverlapping()

Return true if the overlapping property has been set. See SearchIterator.setOverlapping(boolean) for more information.

Returns:

true if the overlapping property has been set, false otherwise

See Also:

SearchIterator.setOverlapping(boolean)

reset

public void reset()

Resets the iteration. Search will begin at the start of the text string if a forward iteration is initiated before a backwards iteration. Otherwise if a backwards iteration is initiated before a forwards iteration, the search will begin at the end of the text string.

first

public final int first()

Returns the first index at which the string text matches the search pattern. The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to the index SearchIterator.DONE.

Returns:

The character index of the first match, or SearchIterator.DONE if there are no matches.

See Also:

SearchIterator.getIndex()

following

public final int following(int position)

Returns the first index equal or greater than position at which the string text matches the search pattern. The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to the index SearchIterator.DONE.

Parameters:

position - where search if to start from.

Returns:

The character index of the first match following position, or SearchIterator.DONE if there are no matches.

Throws:

IndexOutOfBoundsException - If position is less than or greater than the text range for searching.

See Also:

SearchIterator.getIndex()

last

public final int last()

Returns the last index in the target text at which it matches the search pattern. The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to the index SearchIterator.DONE.

Returns:

The index of the first match, or SearchIterator.DONE if there are no matches.

See Also:

SearchIterator.getIndex()

preceding

public final int preceding(int position)

Returns the first index less than position at which the string text matches the search pattern. The iterator is adjusted so that its current index (as returned by SearchIterator.getIndex()) is the match position if one was found. If a match is not found, SearchIterator.DONE will be returned and the iterator will be adjusted to the index SearchIterator.DONE

When the overlapping option (SearchIterator.isOverlapping()) is off, the last index of the result match is always less than position. When the overlapping option is on, the result match may span across position.

Parameters:

position - where search is to start from.

Returns:

The character index of the first match preceding position, or SearchIterator.DONE if there are no matches.

Throws:

IndexOutOfBoundsException - If position is less than or greater than the text range for searching

See Also:

SearchIterator.getIndex()

setMatchLength

protected void setMatchLength(int length)

Sets the length of the most recent match in the target text. Subclasses' handleNext() and handlePrevious() methods should call this after they find a match in the target text.

Parameters:

length - new length to set

See Also:

SearchIterator.handleNext(int), SearchIterator.handlePrevious(int)

handleNext

protected abstract int handleNext(int start)

Abstract method which subclasses override to provide the mechanism for finding the next match in the target text. This allows different subclasses to provide different search algorithms.

If a match is found, the implementation should return the index at which the match starts and should call SearchIterator.setMatchLength(int) with the number of characters in the target text that make up the match. If no match is found, the method should return SearchIterator.DONE.

Parameters:

start - The index in the target text at which the search should start.

Returns:

index at which the match starts, else if match is not found SearchIterator.DONE is returned

See Also:

SearchIterator.setMatchLength(int)

handlePrevious

protected abstract int handlePrevious(int startAt)

Abstract method which subclasses override to provide the mechanism for finding the previous match in the target text. This allows different subclasses to provide different search algorithms.

If a match is found, the implementation should return the index at which the match starts and should call SearchIterator.setMatchLength(int) with the number of characters in the target text that make up the match. If no match is found, the method should return SearchIterator.DONE.

Parameters:

startAt - The index in the target text at which the search should start.

Returns:

index at which the match starts, else if match is not found SearchIterator.DONE is returned

See Also:

SearchIterator.setMatchLength(int)

setElementComparisonType

public void setElementComparisonType(SearchIterator.ElementComparisonType type)

Sets the collation element comparison type.

The default comparison type is SearchIterator.ElementComparisonType.STANDARD_ELEMENT_COMPARISON.

See Also:

SearchIterator.ElementComparisonType, SearchIterator.getElementComparisonType()

getElementComparisonType

public SearchIterator.ElementComparisonType getElementComparisonType()

Returns the collation element comparison type.

See Also:

SearchIterator.ElementComparisonType, SearchIterator.setElementComparisonType(ElementComparisonType)