* 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 * *
{@code
* 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
*
* {@code
* 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.
*
* {@code
* 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);
* }
* }
*
* @since 1.1
* @see StringCharacterIterator
* @see AttributedCharacterIterator
*/
public interface CharacterIterator extends Cloneable {
/**
* 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.
*/
public static final char DONE = '\uFFFF';
/**
* Sets the position to getBeginIndex() and returns the character at that
* position.
*
* @return the first character in the text, or DONE if the text is empty
* @see #getBeginIndex()
*/
public char first();
/**
* Sets the position to getEndIndex()-1 (getEndIndex() if the text is empty) and
* returns the character at that position.
*
* @return the last character in the text, or DONE if the text is empty
* @see #getEndIndex()
*/
public char last();
/**
* Gets the character at the current position (as returned by getIndex()).
*
* @return the character at the current position or DONE if the current position
* is off the end of the text.
* @see #getIndex()
*/
public char current();
/**
* 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.
*
* @return the character at the new position or DONE if the new position is off
* the end of the text range.
*/
public char next();
/**
* 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.
*
* @return the character at the new position or DONE if the current position is
* equal to getBeginIndex().
*/
public char previous();
/**
* Sets the position to the specified position in the text and returns that
* character.
*
* @param position the position within the text. Valid values range from
* getBeginIndex() to getEndIndex(). An IllegalArgumentException
* is thrown if an invalid value is supplied.
* @return the character at the specified position or DONE if the specified
* position is equal to getEndIndex()
*/
public char setIndex(int position);
/**
* Returns the start index of the text.
*
* @return the index at which the text begins.
*/
public int getBeginIndex();
/**
* Returns the end index of the text. This index is the index of the first
* character following the end of the text.
*
* @return the index after the last character in the text
*/
public int getEndIndex();
/**
* Returns the current index.
*
* @return the current index.
*/
public int getIndex();
/**
* Create a copy of this iterator
*
* @return A copy of this
*/
public Object clone();
}