306 lines
12 KiB
Java
306 lines
12 KiB
Java
/*
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* Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang;
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import java.util.NoSuchElementException;
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import java.util.Objects;
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import java.util.PrimitiveIterator;
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import java.util.Spliterator;
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import java.util.Spliterators;
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import java.util.function.IntConsumer;
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import java.util.stream.IntStream;
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import java.util.stream.StreamSupport;
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/**
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* A {@code CharSequence} is a readable sequence of {@code char} values. This
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* interface provides uniform, read-only access to many different kinds of
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* {@code char} sequences.
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* A {@code char} value represents a character in the <i>Basic
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* Multilingual Plane (BMP)</i> or a surrogate. Refer to <a
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* href="Character.html#unicode">Unicode Character Representation</a> for details.
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*
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* <p> This interface does not refine the general contracts of the {@link
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* java.lang.Object#equals(java.lang.Object) equals} and {@link
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* java.lang.Object#hashCode() hashCode} methods. The result of testing two objects
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* that implement {@code CharSequence} for equality is therefore, in general, undefined.
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* Each object may be implemented by a different class, and there
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* is no guarantee that each class will be capable of testing its instances
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* for equality with those of the other. It is therefore inappropriate to use
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* arbitrary {@code CharSequence} instances as elements in a set or as keys in
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* a map. </p>
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*
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* @author Mike McCloskey
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* @since 1.4
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*/
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public interface CharSequence {
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/**
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* Returns the length of this character sequence. The length is the number
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* of 16-bit {@code char}s in the sequence.
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*
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* @return the number of {@code char}s in this sequence
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*/
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int length();
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/**
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* Returns the {@code char} value at the specified index. An index ranges from zero
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* to {@code length() - 1}. The first {@code char} value of the sequence is at
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* index zero, the next at index one, and so on, as for array
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* indexing.
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*
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* <p>If the {@code char} value specified by the index is a
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* <a href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate</a>, the surrogate
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* value is returned.
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*
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* @param index the index of the {@code char} value to be returned
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*
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* @return the specified {@code char} value
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*
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* @throws IndexOutOfBoundsException
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* if the {@code index} argument is negative or not less than
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* {@code length()}
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*/
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char charAt(int index);
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/**
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* Returns {@code true} if this character sequence is empty.
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*
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* @implSpec
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* The default implementation returns the result of calling {@code length() == 0}.
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*
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* @return {@code true} if {@link #length()} is {@code 0}, otherwise
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* {@code false}
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*
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* @since 15
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*/
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default boolean isEmpty() {
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return this.length() == 0;
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}
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/**
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* Returns a {@code CharSequence} that is a subsequence of this sequence.
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* The subsequence starts with the {@code char} value at the specified index and
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* ends with the {@code char} value at index {@code end - 1}. The length
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* (in {@code char}s) of the
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* returned sequence is {@code end - start}, so if {@code start == end}
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* then an empty sequence is returned.
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*
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* @param start the start index, inclusive
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* @param end the end index, exclusive
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*
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* @return the specified subsequence
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*
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* @throws IndexOutOfBoundsException
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* if {@code start} or {@code end} are negative,
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* if {@code end} is greater than {@code length()},
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* or if {@code start} is greater than {@code end}
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*/
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CharSequence subSequence(int start, int end);
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/**
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* Returns a string containing the characters in this sequence in the same
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* order as this sequence. The length of the string will be the length of
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* this sequence.
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*
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* @return a string consisting of exactly this sequence of characters
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*/
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public String toString();
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/**
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* Returns a stream of {@code int} zero-extending the {@code char} values
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* from this sequence. Any char which maps to a <a
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* href="{@docRoot}/java.base/java/lang/Character.html#unicode">surrogate code
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* point</a> is passed through uninterpreted.
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*
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* <p>The stream binds to this sequence when the terminal stream operation
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* commences (specifically, for mutable sequences the spliterator for the
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* stream is <a href="../util/Spliterator.html#binding"><em>late-binding</em></a>).
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* If the sequence is modified during that operation then the result is
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* undefined.
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*
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* @return an IntStream of char values from this sequence
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* @since 1.8
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*/
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public default IntStream chars() {
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class CharIterator implements PrimitiveIterator.OfInt {
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int cur = 0;
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public boolean hasNext() {
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return cur < length();
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}
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public int nextInt() {
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if (hasNext()) {
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return charAt(cur++);
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} else {
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throw new NoSuchElementException();
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}
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}
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@Override
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public void forEachRemaining(IntConsumer block) {
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for (; cur < length(); cur++) {
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block.accept(charAt(cur));
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}
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}
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}
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return StreamSupport.intStream(() ->
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Spliterators.spliterator(
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new CharIterator(),
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length(),
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Spliterator.ORDERED),
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Spliterator.SUBSIZED | Spliterator.SIZED | Spliterator.ORDERED,
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false);
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}
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/**
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* Returns a stream of code point values from this sequence. Any surrogate
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* pairs encountered in the sequence are combined as if by {@linkplain
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* Character#toCodePoint Character.toCodePoint} and the result is passed
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* to the stream. Any other code units, including ordinary BMP characters,
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* unpaired surrogates, and undefined code units, are zero-extended to
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* {@code int} values which are then passed to the stream.
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*
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* <p>The stream binds to this sequence when the terminal stream operation
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* commences (specifically, for mutable sequences the spliterator for the
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* stream is <a href="../util/Spliterator.html#binding"><em>late-binding</em></a>).
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* If the sequence is modified during that operation then the result is
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* undefined.
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*
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* @return an IntStream of Unicode code points from this sequence
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* @since 1.8
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*/
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public default IntStream codePoints() {
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class CodePointIterator implements PrimitiveIterator.OfInt {
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int cur = 0;
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@Override
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public void forEachRemaining(IntConsumer block) {
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final int length = length();
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int i = cur;
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try {
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while (i < length) {
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char c1 = charAt(i++);
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if (!Character.isHighSurrogate(c1) || i >= length) {
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block.accept(c1);
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} else {
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char c2 = charAt(i);
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if (Character.isLowSurrogate(c2)) {
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i++;
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block.accept(Character.toCodePoint(c1, c2));
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} else {
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block.accept(c1);
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}
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}
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}
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} finally {
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cur = i;
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}
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}
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public boolean hasNext() {
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return cur < length();
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}
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public int nextInt() {
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final int length = length();
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if (cur >= length) {
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throw new NoSuchElementException();
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}
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char c1 = charAt(cur++);
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if (Character.isHighSurrogate(c1) && cur < length) {
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char c2 = charAt(cur);
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if (Character.isLowSurrogate(c2)) {
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cur++;
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return Character.toCodePoint(c1, c2);
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}
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}
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return c1;
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}
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}
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return StreamSupport.intStream(() ->
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Spliterators.spliteratorUnknownSize(
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new CodePointIterator(),
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Spliterator.ORDERED),
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Spliterator.ORDERED,
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false);
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}
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/**
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* Compares two {@code CharSequence} instances lexicographically. Returns a
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* negative value, zero, or a positive value if the first sequence is lexicographically
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* less than, equal to, or greater than the second, respectively.
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*
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* <p>
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* The lexicographical ordering of {@code CharSequence} is defined as follows.
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* Consider a {@code CharSequence} <i>cs</i> of length <i>len</i> to be a
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* sequence of char values, <i>cs[0]</i> to <i>cs[len-1]</i>. Suppose <i>k</i>
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* is the lowest index at which the corresponding char values from each sequence
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* differ. The lexicographic ordering of the sequences is determined by a numeric
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* comparison of the char values <i>cs1[k]</i> with <i>cs2[k]</i>. If there is
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* no such index <i>k</i>, the shorter sequence is considered lexicographically
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* less than the other. If the sequences have the same length, the sequences are
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* considered lexicographically equal.
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*
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*
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* @param cs1 the first {@code CharSequence}
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* @param cs2 the second {@code CharSequence}
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*
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* @return the value {@code 0} if the two {@code CharSequence} are equal;
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* a negative integer if the first {@code CharSequence}
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* is lexicographically less than the second; or a
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* positive integer if the first {@code CharSequence} is
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* lexicographically greater than the second.
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*
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* @since 11
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*/
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@SuppressWarnings("unchecked")
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public static int compare(CharSequence cs1, CharSequence cs2) {
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if (Objects.requireNonNull(cs1) == Objects.requireNonNull(cs2)) {
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return 0;
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}
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if (cs1.getClass() == cs2.getClass() && cs1 instanceof Comparable) {
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return ((Comparable<Object>) cs1).compareTo(cs2);
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}
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for (int i = 0, len = Math.min(cs1.length(), cs2.length()); i < len; i++) {
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char a = cs1.charAt(i);
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char b = cs2.charAt(i);
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if (a != b) {
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return a - b;
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}
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}
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return cs1.length() - cs2.length();
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}
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}
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