StringSearch

Kotlin |Java

class StringSearch : SearchIterator

kotlin.Any
↳	android.icu.text.SearchIterator
	↳	android.icu.text.StringSearch

StringSearch is a SearchIterator that provides language-sensitive text searching based on the comparison rules defined in a RuleBasedCollator object. StringSearch ensures that language eccentricity can be handled, e.g. for the German collator, characters ß and SS will be matched if case is chosen to be ignored. See the "ICU Collation Design Document" for more information.

There are 2 match options for selection:
Let S' be the sub-string of a text string S between the offsets start and end [start, end].
A pattern string P matches a text string S at the offsets [start, end] if

option 1. Some canonical equivalent of P matches some canonical equivalent
            of S'
  option 2. P matches S' and if P starts or ends with a combining mark,
            there exists no non-ignorable combining mark before or after S?
            in S respectively.

Option 2. is the default.

This search has APIs similar to that of other text iteration mechanisms such as the break iterators in BreakIterator. Using these APIs, it is easy to scan through text looking for all occurrences of a given pattern. This search iterator allows changing of direction by calling a reset followed by a next or previous. Though a direction change can occur without calling reset first, this operation comes with some speed penalty. Match results in the forward direction will match the result matches in the backwards direction in the reverse order

SearchIterator provides APIs to specify the starting position within the text string to be searched, e.g. setIndex, preceding and following. Since the starting position will be set as it is specified, please take note that there are some danger points at which the search may render incorrect results:

In the midst of a substring that requires normalization.
If the following match is to be found, the position should not be the second character which requires swapping with the preceding character. Vice versa, if the preceding match is to be found, the position to search from should not be the first character which requires swapping with the next character. E.g certain Thai and Lao characters require swapping.
If a following pattern match is to be found, any position within a contracting sequence except the first will fail. Vice versa if a preceding pattern match is to be found, an invalid starting point would be any character within a contracting sequence except the last.

A BreakIterator can be used if only matches at logical breaks are desired. Using a BreakIterator will only give you results that exactly matches the boundaries given by the BreakIterator. For instance the pattern "e" will not be found in the string "\u00e9" if a character break iterator is used.

Options are provided to handle overlapping matches. E.g. In English, overlapping matches produces the result 0 and 2 for the pattern "abab" in the text "ababab", where mutually exclusive matches only produces the result of 0.

Options are also provided to implement "asymmetric search" as described in UTS #10 Unicode Collation Algorithm, specifically the ElementComparisonType values.

Though collator attributes will be taken into consideration while performing matches, there are no APIs here for setting and getting the attributes. These attributes can be set by getting the collator from getCollator and using the APIs in RuleBasedCollator. Lastly to update StringSearch to the new collator attributes, reset has to be called.

Restriction:
Currently there are no composite characters that consists of a character with combining class > 0 before a character with combining class == 0. However, if such a character exists in the future, StringSearch does not guarantee the results for option 1.

Consult the SearchIterator documentation for information on and examples of how to use instances of this class to implement text searching.

Note, StringSearch is not to be subclassed.

Summary

Inherited constants

From class SearchIterator

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.

Public constructors
`StringSearch(pattern: String!, target: CharacterIterator!, collator: RuleBasedCollator!, breakiter: BreakIterator!)` Initializes the iterator to use the language-specific rules defined in the argument collator to search for argument pattern in the argument target text.
`StringSearch(pattern: String!, target: CharacterIterator!, collator: RuleBasedCollator!)` Initializes the iterator to use the language-specific rules defined in the argument collator to search for argument pattern in the argument target text.
`StringSearch(pattern: String!, target: CharacterIterator!, locale: Locale!)` Initializes the iterator to use the language-specific rules and break iterator rules defined in the argument locale to search for argument pattern in the argument target text.
`StringSearch(pattern: String!, target: CharacterIterator!, locale: ULocale!)` Initializes the iterator to use the language-specific rules and break iterator rules defined in the argument locale to search for argument pattern in the argument target text.
`StringSearch(pattern: String!, target: String!)` Initializes the iterator to use the language-specific rules and break iterator rules defined in the default locale to search for argument pattern in the argument target text.

Public methods
RuleBasedCollator!	`getCollator()` Gets the `RuleBasedCollator` used for the language rules.
Int	`getIndex()` Return the current index in the text being searched.
String!	`getPattern()` Returns the pattern for which StringSearch is searching for.
Boolean	`isCanonical()` Determines whether canonical matches (option 1, as described in the class documentation) is set.
Unit	`reset()` Resets the iteration.
Unit	`setCanonical(allowCanonical: Boolean)` Set the canonical match mode.
Unit	`setCollator(collator: RuleBasedCollator!)` Sets the `RuleBasedCollator` to be used for language-specific searching.
Unit	`setIndex(position: Int)` Sets the position in the target text at which the next search will start.
Unit	`setPattern(pattern: String!)` Set the pattern to search for.
Unit	`setTarget(text: CharacterIterator!)` Set the target text to be searched.

Protected methods
Int	`handleNext(position: Int)` Abstract method which subclasses override to provide the mechanism for finding the next match in the target text.
Int	`handlePrevious(position: Int)` Abstract method which subclasses override to provide the mechanism for finding the previous match in the target text.

Inherited functions

From class SearchIterator

`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 `getIndex()`) 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 index `DONE`.
`Int`	`following(position: Int)` 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 `getIndex()`) 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 index `DONE`.
`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 `setBreakIterator`. If the `BreakIterator` has not been set, null will be returned. See `setBreakIterator` for more information.
`SearchIterator.ElementComparisonType!`	`getElementComparisonType()` Returns the collation element comparison type.
`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 `first`, `next`, `previous`, or `last`. Just after construction, or after a searching method returns `DONE`, this method will return 0.
`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 `first`, `next`, `previous`, or `last`. Just after construction, or after a searching method returns `DONE`, this method will return `DONE`. Use `getMatchLength` to get the matched string length.
`String!`	`getMatchedText()` Returns the text that was matched by the most recent call to `first`, `next`, `previous`, or `last`. If the iterator is not pointing at a valid match (e.g. just after construction or after `DONE` has been returned, returns an empty string.
`CharacterIterator!`	`getTarget()` Return the string text to be searched.
`Boolean`	`isOverlapping()` Return true if the overlapping property has been set. See `setOverlapping(boolean)` for more information.
`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 `getIndex`) 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 index `DONE`.
`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 `getIndex`) 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.
`Int`	`preceding(position: Int)` 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 `getIndex`) 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 index `DONE` 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.
`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 `getIndex`) 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 index `DONE`.
`Unit`	`setBreakIterator(breakiter: BreakIterator!)` Set the BreakIterator that will be used to restrict the points at which matches are detected.
`Unit`	`setElementComparisonType(type: SearchIterator.ElementComparisonType!)` Sets the collation element comparison type. The default comparison type is `ElementComparisonType#STANDARD_ELEMENT_COMPARISON`.
`Unit`	`setMatchLength(length: Int)` 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.
`Unit`	`setOverlapping(allowOverlap: Boolean)` Determines whether overlapping matches are returned. See the class documentation for more information about overlapping matches. The default setting of this property is false

Inherited properties

From class SearchIterator

BreakIterator!

breakIterator

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

Int

matchLength

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

CharacterIterator!

targetText

Target text for searching.

Parameters
`pattern`	String!: text to look for.
`target`	CharacterIterator!: target text to search for pattern.
`collator`	RuleBasedCollator!: `RuleBasedCollator` that defines the language rules
`breakiter`	BreakIterator!: A `BreakIterator` that is used to determine the boundaries of a logical match. This argument can be null.

StringSearch

Summary

Public constructors

StringSearch

StringSearch

StringSearch

StringSearch

StringSearch

Public methods

getCollator

getIndex

getPattern

isCanonical

reset

setCanonical

setCollator

setIndex

setPattern

setTarget

Protected methods

handleNext

handlePrevious