Class SearchIterator
- Direct Known Subclasses:
StringSearch
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());
}
- Author:
- Laura Werner, synwee
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic enum
Option to control how collation elements are compared. -
Field Summary
FieldsModifier and TypeFieldDescriptionprotected BreakIterator
The BreakIterator to define the boundaries of a logical match.static final int
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
Length of the most current match in target text.protected CharacterIterator
Target text for searching. -
Constructor Summary
ConstructorsModifierConstructorDescriptionprotected
SearchIterator
(CharacterIterator target, BreakIterator breaker) Protected constructor for use by subclasses. -
Method Summary
Modifier and TypeMethodDescriptionfinal int
first()
Returns the first index at which the string text matches the search pattern.final int
following
(int position) Returns the first index equal or greater than position at which the string text matches the search pattern.Returns the BreakIterator that is used to restrict the indexes at which matches are detected.Returns the collation element comparison type.abstract int
getIndex()
Return the current index in the text being searched.Returns the text that was matched by the most recent call tofirst()
,next()
,previous()
, orlast()
.int
Returns the length of text in the string which matches the search pattern.int
Returns the index to the match in the text string that was searched.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
Return true if the overlapping property has been set.final 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 bygetIndex()
) is the match position if one was found.final 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
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.protected void
Deprecated.This API is ICU internal only.void
setOverlapping
(boolean allowOverlap) Determines whether overlapping matches are returned.void
setTarget
(CharacterIterator text) Set the target text to be searched.
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Field Details
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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:
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targetText
Target text for searching.- See Also:
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matchLength
protected int matchLengthLength of the most current match in target text. Value 0 is the default value.- See Also:
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DONE
public static final int DONEDONE 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:
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Constructor Details
-
SearchIterator
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 andBreakIterator
.- Parameters:
target
- The target text to be searched.breaker
- ABreakIterator
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:
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Method Details
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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:
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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:
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setBreakIterator
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 theBreakIterator
, the match will be rejected and another will be searched for. If this parameter is null, no break detection is attempted.- See Also:
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setTarget
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:
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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 tofirst()
,next()
,previous()
, orlast()
. Just after construction, or after a searching method returnsDONE
, this method will returnDONE
.Use
getMatchLength()
to get the matched string length.- Returns:
- index of a substring within the text string that is being searched.
- See Also:
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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),DONE
is returned.- Returns:
- current index in the text being searched.
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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 tofirst()
,next()
,previous()
, orlast()
. Just after construction, or after a searching method returnsDONE
, 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:
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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 tosetBreakIterator(com.ibm.icu.text.BreakIterator)
. If theBreakIterator
has not been set, null will be returned. SeesetBreakIterator(com.ibm.icu.text.BreakIterator)
for more information.- Returns:
- the BreakIterator set to restrict logic matches
- See Also:
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getTarget
Return the string text to be searched.- Returns:
- text string to be searched.
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getMatchedText
Returns the text that was matched by the most recent call tofirst()
,next()
,previous()
, orlast()
. If the iterator is not pointing at a valid match (e.g. just after construction or afterDONE
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:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,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
DONE
if there are no more matches. - See Also:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,DONE
will be returned and the iterator will be adjusted to the indexDONE
.- Returns:
- The index of the previous match before the current position,
or
DONE
if there are no more matches. - See Also:
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isOverlapping
public boolean isOverlapping()Return true if the overlapping property has been set. SeesetOverlapping(boolean)
for more information.- Returns:
- true if the overlapping property has been set, false otherwise
- See Also:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,DONE
will be returned and the iterator will be adjusted to the indexDONE
.- Returns:
- The character index of the first match, or
DONE
if there are no matches. - See Also:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,DONE
will be returned and the iterator will be adjusted to the indexDONE
.- Parameters:
position
- where search if to start from.- Returns:
- The character index of the first match following
position, or
DONE
if there are no matches. - Throws:
IndexOutOfBoundsException
- If position is less than or greater than the text range for searching.- See Also:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,DONE
will be returned and the iterator will be adjusted to the indexDONE
.- Returns:
- The index of the first match, or
DONE
if there are no matches. - See Also:
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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 bygetIndex()
) is the match position if one was found. If a match is not found,DONE
will be returned and the iterator will be adjusted to the indexDONE
When the overlapping option (
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
DONE
if there are no matches. - Throws:
IndexOutOfBoundsException
- If position is less than or greater than the text range for searching- See Also:
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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:
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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
setMatchLength(int)
with the number of characters in the target text that make up the match. If no match is found, the method should returnDONE
.- 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
DONE
is returned - See Also:
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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
setMatchLength(int)
with the number of characters in the target text that make up the match. If no match is found, the method should returnDONE
.- 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
DONE
is returned - See Also:
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setMatchNotFound
Deprecated.This API is ICU internal only. -
setElementComparisonType
Sets the collation element comparison type.The default comparison type is
SearchIterator.ElementComparisonType.STANDARD_ELEMENT_COMPARISON
.- See Also:
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getElementComparisonType
Returns the collation element comparison type.- See Also:
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