java.text
Class CollationElementIterator

java.lang.Object
  java.text.CollationElementIterator

public final class CollationElementIterator

extends Object

The CollationElementIterator class is used as an iterator to walk through each character of an international string. Use the iterator to return the ordering priority of the positioned character. The ordering priority of a character, which we refer to as a key, defines how a character is collated in the given collation object.

For example, consider the following in Spanish:

 "ca" -> the first key is key('c') and second key is key('a').
 "cha" -> the first key is key('ch') and second key is key('a').
 

And in German,

 "äb"-> the first key is key('a'), the second key is key('e'), and
 the third key is key('b').
 

The key of a character is an integer composed of primary order(short), secondary order(byte), and tertiary order(byte). Java strictly defines the size and signedness of its primitive data types. Therefore, the static functions primaryOrder, secondaryOrder, and tertiaryOrder return int, short, and short respectively to ensure the correctness of the key value.

Example of the iterator usage,

  String testString = "This is a test";
  RuleBasedCollator ruleBasedCollator = (RuleBasedCollator)Collator.getInstance();
  CollationElementIterator collationElementIterator = ruleBasedCollator.getCollationElementIterator(testString);
  int primaryOrder = CollationElementIterator.primaryOrder(collationElementIterator.next());
 

CollationElementIterator.next returns the collation order of the next character. A collation order consists of primary order, secondary order and tertiary order. The data type of the collation order is int. The first 16 bits of a collation order is its primary order; the next 8 bits is the secondary order and the last 8 bits is the tertiary order.

Author:

Helena Shih, Laura Werner, Richard Gillam

See Also:

Collator, RuleBasedCollator

Field Summary

private int[]	buffer
private int	expIndex
private StringBuffer	key
static int	NULLORDER Null order which indicates the end of string is reached by the cursor.
private RBCollationTables	ordering
private RuleBasedCollator	owner
private int	swapOrder
private sun.text.Normalizer	text
(package private) static int	UNMAPPEDCHARVALUE

Constructor Summary

(package private)	CollationElementIterator(CharacterIterator sourceText, RuleBasedCollator owner) CollationElementIterator constructor.
(package private)	CollationElementIterator(String sourceText, RuleBasedCollator owner) CollationElementIterator constructor.

Method Summary

int	getMaxExpansion(int order) Return the maximum length of any expansion sequences that end with the specified comparison order.
int	getOffset() Returns the character offset in the original text corresponding to the next collation element.
(package private) static boolean	isIgnorable(int order) Check if a comparison order is ignorable.
private static boolean	isLaoBaseConsonant(char ch) Determine if a character is a Lao base consonant
private static boolean	isLaoPreVowel(char ch) Determine if a character is a Lao vowel (which sorts after its base consonant).
private static boolean	isThaiBaseConsonant(char ch) Determine if a character is a Thai base consonant
private static boolean	isThaiPreVowel(char ch) Determine if a character is a Thai vowel (which sorts after its base consonant).
private int[]	makeReorderedBuffer(char colFirst, int lastValue, int[] lastExpansion, boolean forward) This method produces a buffer which contains the collation elements for the two characters, with colFirst's values preceding another character's.
int	next() Get the next collation element in the string.
private int	nextContractChar(char ch) Get the ordering priority of the next contracting character in the string.
private int	prevContractChar(char ch) Get the ordering priority of the previous contracting character in the string.
int	previous() Get the previous collation element in the string.
static int	primaryOrder(int order) Return the primary component of a collation element.
void	reset() Resets the cursor to the beginning of the string.
static short	secondaryOrder(int order) Return the secondary component of a collation element.
void	setOffset(int newOffset) Sets the iterator to point to the collation element corresponding to the specified character (the parameter is a CHARACTER offset in the original string, not an offset into its corresponding sequence of collation elements).
void	setText(CharacterIterator source) Set a new string over which to iterate.
void	setText(String source) Set a new string over which to iterate.
(package private) int	strengthOrder(int order) Get the comparison order in the desired strength.
static short	tertiaryOrder(int order) Return the tertiary component of a collation element.

Methods inherited from class java.lang.Object

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

Field Detail

NULLORDER

public static final int NULLORDER

Null order which indicates the end of string is reached by the cursor.

See Also:

Constant Field Values

UNMAPPEDCHARVALUE

static final int UNMAPPEDCHARVALUE

See Also:

Constant Field Values

text

private sun.text.Normalizer text

buffer

private int[] buffer

expIndex

private int expIndex

key

private StringBuffer key

swapOrder

private int swapOrder

ordering

private RBCollationTables ordering

owner

private RuleBasedCollator owner

Constructor Detail

CollationElementIterator

CollationElementIterator(String sourceText,
                         RuleBasedCollator owner)

CollationElementIterator constructor. This takes the source string and the collation object. The cursor will walk thru the source string based on the predefined collation rules. If the source string is empty, NULLORDER will be returned on the calls to next().

Parameters:

sourceText - the source string.

CollationElementIterator

CollationElementIterator(CharacterIterator sourceText,
                         RuleBasedCollator owner)

CollationElementIterator constructor. This takes the source string and the collation object. The cursor will walk thru the source string based on the predefined collation rules. If the source string is empty, NULLORDER will be returned on the calls to next().

Parameters:

sourceText - the source string.

Method Detail

reset

public void reset()

Resets the cursor to the beginning of the string. The next call to next() will return the first collation element in the string.

next

public int next()

Get the next collation element in the 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.

previous

public int previous()

Get the previous collation element in the 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.

Since:

1.2

primaryOrder

public static final int primaryOrder(int order)

Return the primary component of a collation element.

Parameters:

order - the collation element

Returns:

the element's primary component

secondaryOrder

public static final short secondaryOrder(int order)

Return the secondary component of a collation element.

Parameters:

order - the collation element

Returns:

the element's secondary component

tertiaryOrder

public static final short tertiaryOrder(int order)

Return the tertiary component of a collation element.

Parameters:

order - the collation element

Returns:

the element's tertiary component

strengthOrder

final int strengthOrder(int order)

Get the comparison order in the desired strength. Ignore the other differences.

Parameters:

order - The order value

setOffset

public void setOffset(int newOffset)

Sets the iterator to point to the collation element corresponding to the specified character (the parameter is a CHARACTER offset in the original string, not an offset into its corresponding sequence of collation elements). The value returned by the next call to next() will be the collation element corresponding to the specified position in the text. If that position is in the middle of a contracting character sequence, the result of the next call to next() is the collation element for that sequence. This means that getOffset() is not guaranteed to return the same value as was passed to a preceding call to setOffset().

Parameters:

newOffset - The new character offset into the original text.

Since:

1.2

getOffset

public int getOffset()

Returns the character offset in the original text corresponding to the next collation element. (That is, getOffset() returns the position in the text corresponding to the collation element that will be returned by the next call to next().) This value will always be the index of the FIRST character corresponding to the collation element (a contracting character sequence is when two or more characters all correspond to the same collation element). This means if you do setOffset(x) followed immediately by getOffset(), getOffset() won't necessarily return x.

Returns:

The character offset in the original text corresponding to the collation element that will be returned by the next call to next().

Since:

1.2

getMaxExpansion

public int getMaxExpansion(int order)

Return the maximum length of any expansion sequences that end with the specified comparison order.

Parameters:

order - a collation order returned by previous or next.

Returns:

the maximum length of any expansion sequences ending with the specified order.

Since:

1.2

setText

public void setText(String source)

Set a new string over which to iterate.

Parameters:

source - the new source text

Since:

1.2

setText

public void setText(CharacterIterator source)

Set a new string over which to iterate.

Parameters:

source - the new source text.

Since:

1.2

isThaiPreVowel

private static final boolean isThaiPreVowel(char ch)

Determine if a character is a Thai vowel (which sorts after its base consonant).

isThaiBaseConsonant

private static final boolean isThaiBaseConsonant(char ch)

Determine if a character is a Thai base consonant

isLaoPreVowel

private static final boolean isLaoPreVowel(char ch)

Determine if a character is a Lao vowel (which sorts after its base consonant).

isLaoBaseConsonant

private static final boolean isLaoBaseConsonant(char ch)

Determine if a character is a Lao base consonant

makeReorderedBuffer

private int[] makeReorderedBuffer(char colFirst,
                                  int lastValue,
                                  int[] lastExpansion,
                                  boolean forward)

This method produces a buffer which contains the collation elements for the two characters, with colFirst's values preceding another character's. Presumably, the other character precedes colFirst in logical order (otherwise you wouldn't need this method would you?). The assumption is that the other char's value(s) have already been computed. If this char has a single element it is passed to this method as lastValue, and lastExpansion is null. If it has an expansion it is passed in lastExpansion, and colLastValue is ignored.

isIgnorable

static final boolean isIgnorable(int order)

Check if a comparison order is ignorable.

Returns:

true if a character is ignorable, false otherwise.

nextContractChar

private int nextContractChar(char ch)

Get the ordering priority of the next contracting character in the string.

Parameters:

ch - the starting character of a contracting character token

Returns:

the next contracting character's ordering. Returns NULLORDER if the end of string is reached.

prevContractChar

private int prevContractChar(char ch)

Get the ordering priority of the previous contracting character in the string.

Parameters:

ch - the starting character of a contracting character token

Returns:

the next contracting character's ordering. Returns NULLORDER if the end of string is reached.