OpenJDK 27 · java.text.CharacterIterator · APIdia, the JavaDoc alternative

This interface defines a protocol for bidirectional iteration over text. The iterator iterates over a bounded sequence of characters. Characters are indexed with values beginning with the value returned by getBeginIndex() and continuing through the value returned by getEndIndex()-1.

Iterators maintain a current character index, whose valid range is from getBeginIndex() to getEndIndex(); the value getEndIndex() is included to allow handling of zero-length text ranges and for historical reasons. The current index can be retrieved by calling getIndex() and set directly by calling setIndex(), first(), and last().

The methods previous() and next() are used for iteration. They return DONE if they would move outside the range from getBeginIndex() to getEndIndex() -1, signaling that the iterator has reached the end of the sequence. DONE is also returned by other methods to indicate that the current index is outside this range.

Examples:

Traverse the text from start to finish

public void traverseForward(CharacterIterator iter) {
    for (char c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {
        processChar(c);
    }
}

Traverse the text backwards, from end to start

public void traverseBackward(CharacterIterator iter) {
    for (char c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {
        processChar(c);
    }
}

Traverse both forward and backward from a given position in the text. Calls to notBoundary() in this example represents some additional stopping criteria.

public void traverseOut(CharacterIterator iter, int pos) {
    for (char c = iter.setIndex(pos);
             c != CharacterIterator.DONE && notBoundary(c);
             c = iter.next()) {
    }
    int end = iter.getIndex();
    for (char c = iter.setIndex(pos);
            c != CharacterIterator.DONE && notBoundary(c);
            c = iter.previous()) {
    }
    int start = iter.getIndex();
    processSection(start, end);
}

Field Summary

Modifier and Type	Field and Description
public static final char	DONE Constant that is returned when the iterator has reached either the end or the beginning of the text.

Method Summary

Modifier and Type	Method and Description
public Object	Returns: A copy of this clone() Create a copy of this iterator
public char	Returns: the character at the current position or DONE if the current position is off the end of the text. current() Gets the character at the current position (as returned by getIndex()).
public char	Returns: the first character in the text, or DONE if the text is empty first() Sets the position to getBeginIndex() and returns the character at that position.
public int	Returns: the index at which the text begins. getBeginIndex() Returns the start index of the text.
public int	Returns: the index after the last character in the text getEndIndex() Returns the end index of the text.
public int	Returns: the current index. getIndex() Returns the current index.
public char	Returns: the last character in the text, or DONE if the text is empty last() Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty) and returns the character at that position.
public char	Returns: the character at the new position or DONE if the new position is off the end of the text range. next() Increments the iterator's index by one and returns the character at the new index.
public char	Returns: the character at the new position or DONE if the current position is equal to getBeginIndex(). previous() Decrements the iterator's index by one and returns the character at the new index.
public char	Returns: the character at the specified position or DONE if the specified position is equal to getEndIndex() setIndex(int the position within the text. Valid values range from getBeginIndex() to getEndIndex(). An IllegalArgumentException is thrown if an invalid value is supplied. position) Sets the position to the specified position in the text and returns that character.

Field Detail

DONE	back to summary
public static final char DONE Constant that is returned when the iterator has reached either the end or the beginning of the text. The value is '\\uFFFF', the "not a character" value which should not occur in any valid Unicode string.

Method Detail

clone	back to summary
public Object clone() Create a copy of this iterator Returns:Object A copy of this

clone

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public Object clone()

Create a copy of this iterator

Returns:Object: A copy of this

current back to summary

current	back to summary
public char current() Gets the character at the current position (as returned by getIndex()). Returns:char the character at the current position or DONE if the current position is off the end of the text. See Also `getIndex()`

public char current()

Gets the character at the current position (as returned by getIndex()).

Returns:char: the character at the current position or DONE if the current position is off the end of the text.
See Also: getIndex()

first back to summary

first	back to summary
public char first() Sets the position to getBeginIndex() and returns the character at that position. Returns:char the first character in the text, or DONE if the text is empty See Also `getBeginIndex()`

public char first()

Sets the position to getBeginIndex() and returns the character at that position.

Returns:char: the first character in the text, or DONE if the text is empty
See Also: getBeginIndex()

getBeginIndex	back to summary
public int getBeginIndex() Returns the start index of the text. Returns:int the index at which the text begins.

getBeginIndex

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public int getBeginIndex()

Returns the start index of the text.

Returns:int: the index at which the text begins.

getEndIndex	back to summary
public int getEndIndex() Returns the end index of the text. This index is the index of the first character following the end of the text. Returns:int the index after the last character in the text

getEndIndex

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public int getEndIndex()

Returns the end index of the text. This index is the index of the first character following the end of the text.

Returns:int: the index after the last character in the text

getIndex	back to summary
public int getIndex() Returns the current index. Returns:int the current index.

getIndex

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public int getIndex()

Returns the current index.

Returns:int: the current index.

last back to summary

last	back to summary
public char last() Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty) and returns the character at that position. Returns:char the last character in the text, or DONE if the text is empty See Also `getEndIndex()`

public char last()

Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty) and returns the character at that position.

Returns:char: the last character in the text, or DONE if the text is empty
See Also: getEndIndex()

next	back to summary
public char next() Increments the iterator's index by one and returns the character at the new index. If the resulting index is greater or equal to getEndIndex(), the current index is reset to getEndIndex() and a value of DONE is returned. Returns:char the character at the new position or DONE if the new position is off the end of the text range.

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public char next()

Increments the iterator's index by one and returns the character at the new index. If the resulting index is greater or equal to getEndIndex(), the current index is reset to getEndIndex() and a value of DONE is returned.

Returns:char: the character at the new position or DONE if the new position is off the end of the text range.

previous	back to summary
public char previous() Decrements the iterator's index by one and returns the character at the new index. If the current index is getBeginIndex(), the index remains at getBeginIndex() and a value of DONE is returned. Returns:char the character at the new position or DONE if the current position is equal to getBeginIndex().

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public char previous()

Decrements the iterator's index by one and returns the character at the new index. If the current index is getBeginIndex(), the index remains at getBeginIndex() and a value of DONE is returned.

Returns:char: the character at the new position or DONE if the current position is equal to getBeginIndex().

setIndex	back to summary
public char setIndex(int position) Sets the position to the specified position in the text and returns that character. Parameters position:int the position within the text. Valid values range from getBeginIndex() to getEndIndex(). An IllegalArgumentException is thrown if an invalid value is supplied. Returns:char the character at the specified position or DONE if the specified position is equal to getEndIndex()

setIndex

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public char setIndex(int position)

Sets the position to the specified position in the text and returns that character.

Parameters

position:int: the position within the text. Valid values range from getBeginIndex() to getEndIndex(). An IllegalArgumentException is thrown if an invalid value is supplied.

Returns:char

the character at the specified position or DONE if the specified position is equal to getEndIndex()

public Interface CharacterIterator

Field Summary

Method Summary

Field Detail

Method Detail