CharSequence
public
interface
CharSequence
| java.lang.CharSequence |
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.
Summary
Public methods | |
|---|---|
abstract
char
|
charAt(int index)
Returns the |
default
IntStream
|
chars()
Returns a stream of |
default
IntStream
|
codePoints()
Returns a stream of code point values from this sequence. |
static
int
|
compare(CharSequence cs1, CharSequence cs2)
Compares two |
default
boolean
|
isEmpty()
Returns |
abstract
int
|
length()
Returns the length of this character sequence. |
abstract
CharSequence
|
subSequence(int start, int end)
Returns a |
abstract
String
|
toString()
Returns a string containing the characters in this sequence in the same order as this sequence. |
Public methods
charAt
public abstract char charAt (int index)
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.
| Parameters | |
|---|---|
index |
int: the index of the char value to be returned |
| Returns | |
|---|---|
char |
the specified char value |
| Throws | |
|---|---|
IndexOutOfBoundsException |
if the index argument is negative or not less than
length() |
chars
public IntStream chars ()
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 | |
|---|---|
IntStream |
an IntStream of char values from this sequence |
codePoints
public IntStream codePoints ()
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 | |
|---|---|
IntStream |
an IntStream of Unicode code points from this sequence |
compare
public static int compare (CharSequence cs1, CharSequence cs2)
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.
| Parameters | |
|---|---|
cs1 |
CharSequence: the first CharSequence |
cs2 |
CharSequence: the second CharSequence |
| Returns | |
|---|---|
int |
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. |
isEmpty
public boolean isEmpty ()
Returns true if this character sequence is empty.
Implementation Requirements:
- The default implementation returns the result of calling
length() == 0.
| Returns | |
|---|---|
boolean |
true if length() is 0, otherwise
false |
length
public abstract int length ()
Returns the length of this character sequence. The length is the number
of 16-bit chars in the sequence.
| Returns | |
|---|---|
int |
the number of chars in this sequence |
subSequence
public abstract CharSequence subSequence (int start, int end)
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.
| Parameters | |
|---|---|
start |
int: the start index, inclusive |
end |
int: the end index, exclusive |
| Returns | |
|---|---|
CharSequence |
the specified subsequence |
| Throws | |
|---|---|
IndexOutOfBoundsException |
if start or end are negative,
if end is greater than length(),
or if start is greater than end |
toString
public abstract String toString ()
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 | |
|---|---|
String |
a string consisting of exactly this sequence of characters |