Back to index...

	/*
	* Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.lang;

	import java.util.NoSuchElementException;
	import java.util.Objects;
	import java.util.PrimitiveIterator;
	import java.util.Spliterator;
	import java.util.Spliterators;
	import java.util.function.IntConsumer;
	import java.util.stream.IntStream;
	import java.util.stream.StreamSupport;

	/**
	* A {@code CharSequence} is a readable sequence of {@code char} values. This
	* interface provides uniform, read-only access to many different kinds of
	* {@code char} sequences.
	* A {@code char} value represents a character in the <i>Basic
	* Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
	* href="Character.html#unicode">Unicode Character Representation</a> for details.
	*
	* <p> This interface does not refine the general contracts of the {@link
	* java.lang.Object#equals(java.lang.Object) equals} and {@link
	* java.lang.Object#hashCode() hashCode} methods. The result of testing two objects
	* that implement {@code CharSequence} for equality is therefore, in general, undefined.
	* Each object may be implemented by a different class, and there
	* is no guarantee that each class will be capable of testing its instances
	* for equality with those of the other. It is therefore inappropriate to use
	* arbitrary {@code CharSequence} instances as elements in a set or as keys in
	* a map. </p>
	*
	* @author Mike McCloskey
	* @since 1.4
	* @spec JSR-51
	*/

	public interface CharSequence {

	/**
	* Returns the length of this character sequence. The length is the number
	* of 16-bit {@code char}s in the sequence.
	*
	* @return the number of {@code char}s in this sequence
	*/
	int length();

	/**
	* Returns the {@code char} value at the specified index. An index ranges from zero
	* to {@code length() - 1}. The first {@code char} value of the sequence is at
	* index zero, the next at index one, and so on, as for array
	* indexing.
	*
	* <p>If the {@code char} value specified by the index is a
	* <a href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate</a>, the surrogate
	* value is returned.
	*
	* @param index the index of the {@code char} value to be returned
	*
	* @return the specified {@code char} value
	*
	* @throws IndexOutOfBoundsException
	* if the {@code index} argument is negative or not less than
	* {@code length()}
	*/
	char charAt(int index);

	/**
	* Returns a {@code CharSequence} that is a subsequence of this sequence.
	* The subsequence starts with the {@code char} value at the specified index and
	* ends with the {@code char} value at index {@code end - 1}. The length
	* (in {@code char}s) of the
	* returned sequence is {@code end - start}, so if {@code start == end}
	* then an empty sequence is returned.
	*
	* @param start the start index, inclusive
	* @param end the end index, exclusive
	*
	* @return the specified subsequence
	*
	* @throws IndexOutOfBoundsException
	* if {@code start} or {@code end} are negative,
	* if {@code end} is greater than {@code length()},
	* or if {@code start} is greater than {@code end}
	*/
	CharSequence subSequence(int start, int end);

	/**
	* Returns a string containing the characters in this sequence in the same
	* order as this sequence. The length of the string will be the length of
	* this sequence.
	*
	* @return a string consisting of exactly this sequence of characters
	*/
	public String toString();

	/**
	* Returns a stream of {@code int} zero-extending the {@code char} values
	* from this sequence. Any char which maps to a <a
	* href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate code
	* point</a> is passed through uninterpreted.
	*
	* <p>The stream binds to this sequence when the terminal stream operation
	* commences (specifically, for mutable sequences the spliterator for the
	* stream is <a href="../util/Spliterator.html#binding"><em>late-binding</em></a>).
	* If the sequence is modified during that operation then the result is
	* undefined.
	*
	* @return an IntStream of char values from this sequence
	* @since 1.8
	*/
	public default IntStream chars() {
	class CharIterator implements PrimitiveIterator.OfInt {
	int cur = 0;

	public boolean hasNext() {
	return cur < length();
	}

	public int nextInt() {
	if (hasNext()) {
	return charAt(cur++);
	} else {
	throw new NoSuchElementException();
	}
	}

	@Override
	public void forEachRemaining(IntConsumer block) {
	for (; cur < length(); cur++) {
	block.accept(charAt(cur));
	}
	}
	}

	return StreamSupport.intStream(() ->
	Spliterators.spliterator(
	new CharIterator(),
	length(),
	Spliterator.ORDERED),
	Spliterator.SUBSIZED \| Spliterator.SIZED \| Spliterator.ORDERED,
	false);
	}

	/**
	* Returns a stream of code point values from this sequence. Any surrogate
	* pairs encountered in the sequence are combined as if by {@linkplain
	* Character#toCodePoint Character.toCodePoint} and the result is passed
	* to the stream. Any other code units, including ordinary BMP characters,
	* unpaired surrogates, and undefined code units, are zero-extended to
	* {@code int} values which are then passed to the stream.
	*
	* <p>The stream binds to this sequence when the terminal stream operation
	* commences (specifically, for mutable sequences the spliterator for the
	* stream is <a href="../util/Spliterator.html#binding"><em>late-binding</em></a>).
	* If the sequence is modified during that operation then the result is
	* undefined.
	*
	* @return an IntStream of Unicode code points from this sequence
	* @since 1.8
	*/
	public default IntStream codePoints() {
	class CodePointIterator implements PrimitiveIterator.OfInt {
	int cur = 0;

	@Override
	public void forEachRemaining(IntConsumer block) {
	final int length = length();
	int i = cur;
	try {
	while (i < length) {
	char c1 = charAt(i++);
	if (!Character.isHighSurrogate(c1) \|\| i >= length) {
	block.accept(c1);
	} else {
	char c2 = charAt(i);
	if (Character.isLowSurrogate(c2)) {
	i++;
	block.accept(Character.toCodePoint(c1, c2));
	} else {
	block.accept(c1);
	}
	}
	}
	} finally {
	cur = i;
	}
	}

	public boolean hasNext() {
	return cur < length();
	}

	public int nextInt() {
	final int length = length();

	if (cur >= length) {
	throw new NoSuchElementException();
	}
	char c1 = charAt(cur++);
	if (Character.isHighSurrogate(c1) && cur < length) {
	char c2 = charAt(cur);
	if (Character.isLowSurrogate(c2)) {
	cur++;
	return Character.toCodePoint(c1, c2);
	}
	}
	return c1;
	}
	}

	return StreamSupport.intStream(() ->
	Spliterators.spliteratorUnknownSize(
	new CodePointIterator(),
	Spliterator.ORDERED),
	Spliterator.ORDERED,
	false);
	}

	/**
	* Compares two {@code CharSequence} instances lexicographically. Returns a
	* negative value, zero, or a positive value if the first sequence is lexicographically
	* less than, equal to, or greater than the second, respectively.
	*
	* <p>
	* The lexicographical ordering of {@code CharSequence} is defined as follows.
	* Consider a {@code CharSequence} <i>cs</i> of length <i>len</i> to be a
	* sequence of char values, <i>cs[0]</i> to <i>cs[len-1]</i>. Suppose <i>k</i>
	* is the lowest index at which the corresponding char values from each sequence
	* differ. The lexicographic ordering of the sequences is determined by a numeric
	* comparison of the char values <i>cs1[k]</i> with <i>cs2[k]</i>. If there is
	* no such index <i>k</i>, the shorter sequence is considered lexicographically
	* less than the other. If the sequences have the same length, the sequences are
	* considered lexicographically equal.
	*
	*
	* @param cs1 the first {@code CharSequence}
	* @param cs2 the second {@code CharSequence}
	*
	* @return the value {@code 0} if the two {@code CharSequence} are equal;
	* a negative integer if the first {@code CharSequence}
	* is lexicographically less than the second; or a
	* positive integer if the first {@code CharSequence} is
	* lexicographically greater than the second.
	*
	* @since 11
	*/
	@SuppressWarnings("unchecked")
	public static int compare(CharSequence cs1, CharSequence cs2) {
	if (Objects.requireNonNull(cs1) == Objects.requireNonNull(cs2)) {
	return 0;
	}

	if (cs1.getClass() == cs2.getClass() && cs1 instanceof Comparable) {
	return ((Comparable<Object>) cs1).compareTo(cs2);
	}

	for (int i = 0, len = Math.min(cs1.length(), cs2.length()); i < len; i++) {
	char a = cs1.charAt(i);
	char b = cs2.charAt(i);
	if (a != b) {
	return a - b;
	}
	}

	return cs1.length() - cs2.length();
	}

	}

Back to index...