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java.lang.Objectcom.ibm.icu.text.CollationElementIterator
public final class CollationElementIterator
CollationElementIterator
is an iterator created by
a RuleBasedCollator to walk through a string. The return result of
each iteration is a 32-bit collation element that defines the
ordering priority of the next character or sequence of characters
in the source string.
For illustration, consider the following in Spanish:
And in German,"ca" -> the first collation element is collation_element('c') and second collation element is collation_element('a'). Since "ch" in Spanish sorts as one entity, the below example returns one collation element for the two characters 'c' and 'h' "cha" -> the first collation element is collation_element('ch') and second collation element is collation_element('a').
Since the character 'æ' is a composed character of 'a' and 'e', the iterator returns two collation elements for the single character 'æ' "æb" -> the first collation element is collation_element('a'), the second collation element is collation_element('e'), and the third collation element is collation_element('b').
For collation ordering comparison, the collation element results can not be compared simply by using basic arithmetric operators, e.g. <, == or >, further processing has to be done. Details can be found in the ICU user guide. An example of using the CollationElementIterator for collation ordering comparison is the class com.ibm.icu.text.StringSearch.
To construct a CollationElementIterator object, users call the method getCollationElementIterator() on a RuleBasedCollator that defines the desired sorting order.
Example:
String testString = "This is a test"; RuleBasedCollator rbc = new RuleBasedCollator("&a<b"); CollationElementIterator iterator = rbc.getCollationElementIterator(testString); int primaryOrder = iterator.IGNORABLE; while (primaryOrder != iterator.NULLORDER) { int order = iterator.next(); if (order != iterator.IGNORABLE && order != iterator.NULLORDER) { // order is valid, not ignorable and we have not passed the end // of the iteration, we do something primaryOrder = CollationElementIterator.primaryOrder(order); System.out.println("Next primary order 0x" + Integer.toHexString(primaryOrder)); } }
This class is not subclassable
Collator
,
RuleBasedCollator
,
StringSearch
Field Summary | |
---|---|
static int |
IGNORABLE
This constant is returned by the iterator in the methods next() and previous() when a collation element result is to be ignored. |
static int |
NULLORDER
This constant is returned by the iterator in the methods next() and previous() when the end or the beginning of the source string has been reached, and there are no more valid collation elements to return. |
Method Summary | |
---|---|
boolean |
equals(Object that)
Tests that argument object is equals to this CollationElementIterator. |
int |
getMaxExpansion(int ce)
Returns the maximum length of any expansion sequence that ends with the specified collation element. |
int |
getOffset()
Returns the character offset in the source string corresponding to the next collation element. |
int |
next()
Get the next collation element in the source string. |
int |
previous()
Get the previous collation element in the source string. |
static int |
primaryOrder(int ce)
Return the primary order of the specified collation element, i.e. the first 16 bits. |
void |
reset()
Resets the cursor to the beginning of the string. |
static int |
secondaryOrder(int ce)
Return the secondary order of the specified collation element, i.e. the 16th to 23th bits, inclusive. |
void |
setOffset(int offset)
Sets the iterator to point to the collation element corresponding to the character at the specified offset. |
void |
setText(CharacterIterator source)
Set a new source string iterator for iteration, and reset the offset to the beginning of the text. |
void |
setText(String source)
Set a new source string for iteration, and reset the offset to the beginning of the text. |
void |
setText(UCharacterIterator source)
Set a new source string iterator for iteration, and reset the offset to the beginning of the text. |
static int |
tertiaryOrder(int ce)
Return the tertiary order of the specified collation element, i.e. the last 8 bits. |
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final int NULLORDER
This constant is returned by the iterator in the methods next() and previous() when the end or the beginning of the source string has been reached, and there are no more valid collation elements to return.
See class documentation for an example of use.
next()
,
previous()
,
Constant Field Valuespublic static final int IGNORABLE
This constant is returned by the iterator in the methods next() and previous() when a collation element result is to be ignored.
See class documentation for an example of use.
next()
,
previous()
,
Constant Field ValuesMethod Detail |
---|
public int getOffset()
Returns the character offset in the source string corresponding to the next collation element. I.e., getOffset() returns the position in the source string corresponding to the collation element that will be returned by the next call to next(). This value could be any of:
setOffset(offset)
sets the index in the middle of
a contraction, getOffset()
returns the index of
the first character in the contraction, which may not be equal
to the original offset that was set. Hence calling getOffset()
immediately after setOffset(offset) does not guarantee that the
original offset set will be returned.)
public int getMaxExpansion(int ce)
Returns the maximum length of any expansion sequence that ends with the specified collation element. If there is no expansion with this collation element as the last element, returns 1.
ce
- a collation element returned by previous() or next().
public void reset()
Resets the cursor to the beginning of the string. The next call to next() or previous() will return the first and last collation element in the string, respectively.
If the RuleBasedCollator used by this iterator has had its attributes changed, calling reset() will reinitialize the iterator to use the new attributes.
public int next()
Get the next collation element in the source string.
This iterator iterates over a sequence of collation elements that were built from the string. Because there isn't necessarily a one-to-one mapping from characters to collation elements, this doesn't mean the same thing as "return the collation element [or ordering priority] of the next character in the string".
This function returns the collation element that the iterator is currently pointing to, and then updates the internal pointer to point to the next element. Previous() updates the pointer first, and then returns the element. This means that when you change direction while iterating (i.e., call next() and then call previous(), or call previous() and then call next()), you'll get back the same element twice.
public int previous()
Get the previous collation element in the source string.
This iterator iterates over a sequence of collation elements that were built from the string. Because there isn't necessarily a one-to-one mapping from characters to collation elements, this doesn't mean the same thing as "return the collation element [or ordering priority] of the previous character in the string".
This function updates the iterator's internal pointer to point to the collation element preceding the one it's currently pointing to and then returns that element, while next() returns the current element and then updates the pointer. This means that when you change direction while iterating (i.e., call next() and then call previous(), or call previous() and then call next()), you'll get back the same element twice.
public static final int primaryOrder(int ce)
ce
- the collation element
public static final int secondaryOrder(int ce)
ce
- the collation element
public static final int tertiaryOrder(int ce)
ce
- the collation element
public void setOffset(int offset)
Sets the iterator to point to the collation element corresponding to the character at the specified offset. The value returned by the next call to next() will be the collation element corresponding to the characters at offset.
If offset is in the middle of a contracting character sequence, the iterator is adjusted to the start of the contracting sequence. This means that getOffset() is not guaranteed to return the same value set by this method.
If the decomposition mode is on, and offset is in the middle of a decomposible range of source text, the iterator may not return a correct result for the next forwards or backwards iteration. The user must ensure that the offset is not in the middle of a decomposible range.
offset
- the character offset into the original source string to
set. Note that this is not an offset into the corresponding
sequence of collation elements.public void setText(String source)
Set a new source string for iteration, and reset the offset to the beginning of the text.
source
- the new source string for iteration.public void setText(UCharacterIterator source)
Set a new source string iterator for iteration, and reset the offset to the beginning of the text.
The source iterator's integrity will be preserved since a new copy will be created for use.
source
- the new source string iterator for iteration.public void setText(CharacterIterator source)
Set a new source string iterator for iteration, and reset the offset to the beginning of the text.
source
- the new source string iterator for iteration.public boolean equals(Object that)
equals
in class Object
that
- object to test if it is equals to this
CollationElementIterator
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