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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 CharSequence is a readable sequence of char values. This interface provides uniform, read-only access to many different kinds of char sequences. A char value represents a character in the Basic
Multilingual Plane (BMP) or a surrogate. Refer to Unicode Character Representation for details.
This interface does not refine the general contracts of the equals and hashCode methods. The result of testing two objects that implement 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 CharSequence instances as elements in a set or as keys in a map.
Author: Mike McCloskey Since: 1.4 @spec JSR-51
/**
* 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 chars in the sequence. Returns: the number of chars in this sequence
/**
* 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 char value at the specified index. An index ranges from zero to length() - 1. The first char value of the sequence is at index zero, the next at index one, and so on, as for array indexing. If the char value specified by the index is a surrogate, the surrogate
value is returned.
Params: - index – the index of the
char value to be returned
Throws: - IndexOutOfBoundsException – if the
index argument is negative or not less than length()
Returns: the specified char value
/**
* 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 true if this character sequence is empty. Implementation Requirements: The default implementation returns the result of calling length() == 0. Returns: true if length() is 0, otherwise falseSince: 15
/**
* Returns {@code true} if this character sequence is empty.
*
* @implSpec
* The default implementation returns the result of calling {@code length() == 0}.
*
* @return {@code true} if {@link #length()} is {@code 0}, otherwise
* {@code false}
*
* @since 15
*/
default boolean isEmpty() {
return this.length() == 0;
}
Returns a CharSequence that is a subsequence of this sequence. The subsequence starts with the char value at the specified index and ends with the char value at index end - 1. The length (in chars) of the returned sequence is end - start, so if start == end then an empty sequence is returned. Params: - start – the start index, inclusive
- end – the end index, exclusive
Throws: - IndexOutOfBoundsException – if
start or end are negative, if end is greater than length(), or if start is greater than end
Returns: the specified subsequence
/**
* 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.
Returns: a string consisting of exactly this sequence of characters
/**
* 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 int zero-extending the char values from this sequence. Any char which maps to a surrogate code
point is passed through uninterpreted.
The stream binds to this sequence when the terminal stream operation
commences (specifically, for mutable sequences the spliterator for the
stream is late-binding).
If the sequence is modified during that operation then the result is
undefined.
Returns: an IntStream of char values from this sequence Since: 1.8
/**
* 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 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 int values which are then passed to the stream. The stream binds to this sequence when the terminal stream operation
commences (specifically, for mutable sequences the spliterator for the
stream is late-binding).
If the sequence is modified during that operation then the result is
undefined.
Returns: an IntStream of Unicode code points from this sequence Since: 1.8
/**
* 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 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. The lexicographical ordering of CharSequence is defined as follows. Consider a CharSequence cs of length len to be a
sequence of char values, cs[0] to cs[len-1]. Suppose k
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 cs1[k] with cs2[k]. If there is
no such index k, the shorter sequence is considered lexicographically
less than the other. If the sequences have the same length, the sequences are
considered lexicographically equal.
Params: - cs1 – the first
CharSequence - cs2 – the second
CharSequence
Returns: the value 0 if the two CharSequence are equal; a negative integer if the first CharSequence is lexicographically less than the second; or a positive integer if the first CharSequence is lexicographically greater than the second. Since: 11
/**
* 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();
}
}