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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
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*
* 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).
*
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*
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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();
}
}