Class StringBuilder
- java.lang.Object
-
- java.lang.StringBuilder
- All Implemented Interfaces:
-
Serializable
,Appendable
,CharSequence
,Comparable<StringBuilder>
public final class StringBuilder extends Object implements Serializable, Comparable<StringBuilder>, CharSequence
A mutable sequence of characters. This class provides an API compatible with StringBuffer
, but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer
in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer
as it will be faster under most implementations.
The principal operations on a StringBuilder
are the append
and insert
methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append
method always adds these characters at the end of the builder; the insert
method adds the characters at a specified point.
For example, if z
refers to a string builder object whose current contents are "start
", then the method call z.append("le")
would cause the string builder to contain "startle
", whereas z.insert(4, "le")
would alter the string builder to contain "starlet
".
In general, if sb refers to an instance of a StringBuilder
, then sb.append(x)
has the same effect as sb.insert(sb.length(), x)
.
Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.
Instances of StringBuilder
are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer
be used.
Unless otherwise noted, passing a null
argument to a constructor or method in this class will cause a NullPointerException
to be thrown.
- API Note:
-
StringBuilder
implementsComparable
but does not overrideequals
. Thus, the natural ordering ofStringBuilder
is inconsistent with equals. Care should be exercised ifStringBuilder
objects are used as keys in aSortedMap
or elements in aSortedSet
. SeeComparable
,SortedMap
, orSortedSet
for more information. - Since:
- 1.5
- See Also:
-
StringBuffer
,String
, Serialized Form
Constructor Summary
Constructor | Description |
---|---|
StringBuilder() | Constructs a string builder with no characters in it and an initial capacity of 16 characters. |
StringBuilder(int capacity) | Constructs a string builder with no characters in it and an initial capacity specified by the |
StringBuilder(CharSequence seq) | Constructs a string builder that contains the same characters as the specified |
StringBuilder(String str) | Constructs a string builder initialized to the contents of the specified string. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
StringBuilder | append(boolean b) | Appends the string representation of the |
StringBuilder | append(char c) | Appends the string representation of the |
StringBuilder | append(char[] str) | Appends the string representation of the |
StringBuilder | append(char[] str,
int offset,
int len) | Appends the string representation of a subarray of the |
StringBuilder | append(double d) | Appends the string representation of the |
StringBuilder | append(float f) | Appends the string representation of the |
StringBuilder | append(int i) | Appends the string representation of the |
StringBuilder | append(long lng) | Appends the string representation of the |
StringBuilder | append(CharSequence s) | Appends the specified character sequence to this |
StringBuilder | append(CharSequence s,
int start,
int end) | Appends a subsequence of the specified |
StringBuilder | append(Object obj) | Appends the string representation of the |
StringBuilder | append(String str) | Appends the specified string to this character sequence. |
StringBuilder | append(StringBuffer sb) | Appends the specified |
StringBuilder | appendCodePoint(int codePoint) | Appends the string representation of the |
int | capacity() | Returns the current capacity. |
char | charAt(int index) | Returns the |
IntStream | chars() | Returns a stream of |
int | codePointAt(int index) | Returns the character (Unicode code point) at the specified index. |
int | codePointBefore(int index) | Returns the character (Unicode code point) before the specified index. |
int | codePointCount(int beginIndex,
int endIndex) | Returns the number of Unicode code points in the specified text range of this sequence. |
IntStream | codePoints() | Returns a stream of code point values from this sequence. |
int | compareTo(StringBuilder another) | Compares two |
StringBuilder | delete(int start,
int end) | Removes the characters in a substring of this sequence. |
StringBuilder | deleteCharAt(int index) | Removes the |
void | ensureCapacity(int minimumCapacity) | Ensures that the capacity is at least equal to the specified minimum. |
void | getChars(int srcBegin,
int srcEnd,
char[] dst,
int dstBegin) | Characters are copied from this sequence into the destination character array |
int | indexOf(String str) | Returns the index within this string of the first occurrence of the specified substring. |
int | indexOf(String str,
int fromIndex) | Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. |
StringBuilder | insert(int offset,
boolean b) | Inserts the string representation of the |
StringBuilder | insert(int offset,
char c) | Inserts the string representation of the |
StringBuilder | insert(int offset,
char[] str) | Inserts the string representation of the |
StringBuilder | insert(int index,
char[] str,
int offset,
int len) | Inserts the string representation of a subarray of the |
StringBuilder | insert(int offset,
double d) | Inserts the string representation of the |
StringBuilder | insert(int offset,
float f) | Inserts the string representation of the |
StringBuilder | insert(int offset,
int i) | Inserts the string representation of the second |
StringBuilder | insert(int offset,
long l) | Inserts the string representation of the |
StringBuilder | insert(int dstOffset,
CharSequence s) | Inserts the specified |
StringBuilder | insert(int dstOffset,
CharSequence s,
int start,
int end) | Inserts a subsequence of the specified |
StringBuilder | insert(int offset,
Object obj) | Inserts the string representation of the |
StringBuilder | insert(int offset,
String str) | Inserts the string into this character sequence. |
int | lastIndexOf(String str) | Returns the index within this string of the last occurrence of the specified substring. |
int | lastIndexOf(String str,
int fromIndex) | Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index. |
int | length() | Returns the length (character count). |
int | offsetByCodePoints(int index,
int codePointOffset) | Returns the index within this sequence that is offset from the given |
StringBuilder | replace(int start,
int end,
String str) | Replaces the characters in a substring of this sequence with characters in the specified |
StringBuilder | reverse() | Causes this character sequence to be replaced by the reverse of the sequence. |
void | setCharAt(int index,
char ch) | The character at the specified index is set to |
void | setLength(int newLength) | Sets the length of the character sequence. |
CharSequence | subSequence(int start,
int end) | Returns a new character sequence that is a subsequence of this sequence. |
String | substring(int start) | Returns a new |
String | substring(int start,
int end) | Returns a new |
void | trimToSize() | Attempts to reduce storage used for the character sequence. |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods declared in interface java.lang.CharSequence
charAt, chars, codePoints, length, subSequence, toString
Constructor Detail
StringBuilder
public StringBuilder()
Constructs a string builder with no characters in it and an initial capacity of 16 characters.
StringBuilder
public StringBuilder(int capacity)
Constructs a string builder with no characters in it and an initial capacity specified by the capacity
argument.
- Parameters:
-
capacity
- the initial capacity. - Throws:
-
NegativeArraySizeException
- if thecapacity
argument is less than0
.
StringBuilder
public StringBuilder(String str)
Constructs a string builder initialized to the contents of the specified string. The initial capacity of the string builder is 16
plus the length of the string argument.
- Parameters:
-
str
- the initial contents of the buffer.
StringBuilder
public StringBuilder(CharSequence seq)
Constructs a string builder that contains the same characters as the specified CharSequence
. The initial capacity of the string builder is 16
plus the length of the CharSequence
argument.
- Parameters:
-
seq
- the sequence to copy.
Method Detail
compareTo
public int compareTo(StringBuilder another)
Compares two StringBuilder
instances lexicographically. This method follows the same rules for lexicographical comparison as defined in the CharSequence.compare(this, another) method.
For finer-grained, locale-sensitive String comparison, refer to Collator
.
- Specified by:
-
compareTo
in interfaceComparable<StringBuilder>
- Parameters:
-
another
- theStringBuilder
to be compared with - Returns:
- the value
0
if thisStringBuilder
contains the same character sequence as that of the argumentStringBuilder
; a negative integer if thisStringBuilder
is lexicographically less than theStringBuilder
argument; or a positive integer if thisStringBuilder
is lexicographically greater than theStringBuilder
argument. - Since:
- 11
append
public StringBuilder append(Object obj)
Appends the string representation of the Object
argument.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(Object)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
obj
- anObject
. - Returns:
- a reference to this object.
append
public StringBuilder append(String str)
Appends the specified string to this character sequence.
The characters of the String
argument are appended, in order, increasing the length of this sequence by the length of the argument. If str
is null
, then the four characters "null"
are appended.
Let n be the length of this character sequence just prior to execution of the append
method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n; otherwise, it is equal to the character at index k-n in the argument str
.
- Parameters:
-
str
- a string. - Returns:
- a reference to this object.
append
public StringBuilder append(StringBuffer sb)
Appends the specified StringBuffer
to this sequence.
The characters of the StringBuffer
argument are appended, in order, to this sequence, increasing the length of this sequence by the length of the argument. If sb
is null
, then the four characters "null"
are appended to this sequence.
Let n be the length of this character sequence just prior to execution of the append
method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n; otherwise, it is equal to the character at index k-n in the argument sb
.
- Parameters:
-
sb
- theStringBuffer
to append. - Returns:
- a reference to this object.
append
public StringBuilder append(CharSequence s)
Description copied from interface: Appendable
Appends the specified character sequence to this Appendable
.
Depending on which class implements the character sequence csq
, the entire sequence may not be appended. For instance, if csq
is a CharBuffer
then the subsequence to append is defined by the buffer's position and limit.
- Specified by:
-
append
in interfaceAppendable
- Parameters:
-
s
- The character sequence to append. Ifcsq
isnull
, then the four characters"null"
are appended to this Appendable. - Returns:
- A reference to this
Appendable
append
public StringBuilder append(CharSequence s, int start, int end)
Appends a subsequence of the specified CharSequence
to this sequence.
Characters of the argument s
, starting at index start
, are appended, in order, to the contents of this sequence up to the (exclusive) index end
. The length of this sequence is increased by the value of end - start
.
Let n be the length of this character sequence just prior to execution of the append
method. Then the character at index k in this character sequence becomes equal to the character at index k in this sequence, if k is less than n; otherwise, it is equal to the character at index k+start-n in the argument s
.
If s
is null
, then this method appends characters as if the s parameter was a sequence containing the four characters "null"
.
- Specified by:
-
append
in interfaceAppendable
- Parameters:
-
s
- the sequence to append. -
start
- the starting index of the subsequence to be appended. -
end
- the end index of the subsequence to be appended. - Returns:
- a reference to this object.
- Throws:
-
IndexOutOfBoundsException
- ifstart
is negative, orstart
is greater thanend
orend
is greater thans.length()
append
public StringBuilder append(char[] str)
Appends the string representation of the char
array argument to this sequence.
The characters of the array argument are appended, in order, to the contents of this sequence. The length of this sequence increases by the length of the argument.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char[])
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
str
- the characters to be appended. - Returns:
- a reference to this object.
append
public StringBuilder append(char[] str, int offset, int len)
Appends the string representation of a subarray of the char
array argument to this sequence.
Characters of the char
array str
, starting at index offset
, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value of len
.
The overall effect is exactly as if the arguments were converted to a string by the method String.valueOf(char[],int,int)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
str
- the characters to be appended. -
offset
- the index of the firstchar
to append. -
len
- the number ofchar
s to append. - Returns:
- a reference to this object.
- Throws:
-
IndexOutOfBoundsException
- ifoffset < 0
orlen < 0
oroffset+len > str.length
append
public StringBuilder append(boolean b)
Appends the string representation of the boolean
argument to the sequence.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(boolean)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
b
- aboolean
. - Returns:
- a reference to this object.
append
public StringBuilder append(char c)
Appends the string representation of the char
argument to this sequence.
The argument is appended to the contents of this sequence. The length of this sequence increases by 1
.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char)
, and the character in that string were then appended
to this character sequence.
- Specified by:
-
append
in interfaceAppendable
- Parameters:
-
c
- achar
. - Returns:
- a reference to this object.
append
public StringBuilder append(int i)
Appends the string representation of the int
argument to this sequence.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(int)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
i
- anint
. - Returns:
- a reference to this object.
append
public StringBuilder append(long lng)
Appends the string representation of the long
argument to this sequence.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(long)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
lng
- along
. - Returns:
- a reference to this object.
append
public StringBuilder append(float f)
Appends the string representation of the float
argument to this sequence.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(float)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
f
- afloat
. - Returns:
- a reference to this object.
append
public StringBuilder append(double d)
Appends the string representation of the double
argument to this sequence.
The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(double)
, and the characters of that string were then appended
to this character sequence.
- Parameters:
-
d
- adouble
. - Returns:
- a reference to this object.
appendCodePoint
public StringBuilder appendCodePoint(int codePoint)
Appends the string representation of the codePoint
argument to this sequence.
The argument is appended to the contents of this sequence. The length of this sequence increases by Character.charCount(codePoint)
.
The overall effect is exactly as if the argument were converted to a char
array by the method Character.toChars(int)
and the character in that array were then appended
to this character sequence.
- Parameters:
-
codePoint
- a Unicode code point - Returns:
- a reference to this object.
- Since:
- 1.5
delete
public StringBuilder delete(int start, int end)
Removes the characters in a substring of this sequence. The substring begins at the specified start
and extends to the character at index end - 1
or to the end of the sequence if no such character exists. If start
is equal to end
, no changes are made.
- Parameters:
-
start
- The beginning index, inclusive. -
end
- The ending index, exclusive. - Returns:
- This object.
- Throws:
-
StringIndexOutOfBoundsException
- ifstart
is negative, greater thanlength()
, or greater thanend
.
deleteCharAt
public StringBuilder deleteCharAt(int index)
Removes the char
at the specified position in this sequence. This sequence is shortened by one char
.
Note: If the character at the given index is a supplementary character, this method does not remove the entire character. If correct handling of supplementary characters is required, determine the number of char
s to remove by calling Character.charCount(thisSequence.codePointAt(index))
, where thisSequence
is this sequence.
- Parameters:
-
index
- Index ofchar
to remove - Returns:
- This object.
- Throws:
-
StringIndexOutOfBoundsException
- if theindex
is negative or greater than or equal tolength()
.
replace
public StringBuilder replace(int start, int end, String str)
Replaces the characters in a substring of this sequence with characters in the specified String
. The substring begins at the specified start
and extends to the character at index end - 1
or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specified String
is inserted at start
. (This sequence will be lengthened to accommodate the specified String if necessary.)
- Parameters:
-
start
- The beginning index, inclusive. -
end
- The ending index, exclusive. -
str
- String that will replace previous contents. - Returns:
- This object.
- Throws:
-
StringIndexOutOfBoundsException
- ifstart
is negative, greater thanlength()
, or greater thanend
.
insert
public StringBuilder insert(int index, char[] str, int offset, int len)
Inserts the string representation of a subarray of the str
array argument into this sequence. The subarray begins at the specified offset
and extends len
char
s. The characters of the subarray are inserted into this sequence at the position indicated by index
. The length of this sequence increases by len
char
s.
- Parameters:
-
index
- position at which to insert subarray. -
str
- Achar
array. -
offset
- the index of the firstchar
in subarray to be inserted. -
len
- the number ofchar
s in the subarray to be inserted. - Returns:
- This object
- Throws:
-
StringIndexOutOfBoundsException
- ifindex
is negative or greater thanlength()
, oroffset
orlen
are negative, or(offset+len)
is greater thanstr.length
.
insert
public StringBuilder insert(int offset, Object obj)
Inserts the string representation of the Object
argument into this character sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(Object)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
obj
- anObject
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, String str)
Inserts the string into this character sequence.
The characters of the String
argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument. If str
is null
, then the four characters "null"
are inserted into this sequence.
The character at index k in the new character sequence is equal to:
- the character at index k in the old character sequence, if k is less than
offset
- the character at index k
-offset
in the argumentstr
, if k is not less thanoffset
but is less thanoffset+str.length()
- the character at index k
-str.length()
in the old character sequence, if k is not less thanoffset+str.length()
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
str
- a string. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, char[] str)
Inserts the string representation of the char
array argument into this sequence.
The characters of the array argument are inserted into the contents of this sequence at the position indicated by offset
. The length of this sequence increases by the length of the argument.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char[])
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
str
- a character array. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int dstOffset, CharSequence s)
Inserts the specified CharSequence
into this sequence.
The characters of the CharSequence
argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument s.
The result of this method is exactly the same as if it were an invocation of this object's insert
(dstOffset, s, 0, s.length()) method.
If s
is null
, then the four characters "null"
are inserted into this sequence.
- Parameters:
-
dstOffset
- the offset. -
s
- the sequence to be inserted - Returns:
- a reference to this object.
- Throws:
-
IndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int dstOffset, CharSequence s, int start, int end)
Inserts a subsequence of the specified CharSequence
into this sequence.
The subsequence of the argument s
specified by start
and end
are inserted, in order, into this sequence at the specified destination offset, moving up any characters originally above that position. The length of this sequence is increased by end - start
.
The character at index k in this sequence becomes equal to:
- the character at index k in this sequence, if k is less than
dstOffset
- the character at index k
+start-dstOffset
in the arguments
, if k is greater than or equal todstOffset
but is less thandstOffset+end-start
- the character at index k
-(end-start)
in this sequence, if k is greater than or equal todstOffset+end-start
The dstOffset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
The start argument must be nonnegative, and not greater than end
.
The end argument must be greater than or equal to start
, and less than or equal to the length of s.
If s
is null
, then this method inserts characters as if the s parameter was a sequence containing the four characters "null"
.
- Parameters:
-
dstOffset
- the offset in this sequence. -
s
- the sequence to be inserted. -
start
- the starting index of the subsequence to be inserted. -
end
- the end index of the subsequence to be inserted. - Returns:
- a reference to this object.
- Throws:
-
IndexOutOfBoundsException
- ifdstOffset
is negative or greater thanthis.length()
, orstart
orend
are negative, orstart
is greater thanend
orend
is greater thans.length()
insert
public StringBuilder insert(int offset, boolean b)
Inserts the string representation of the boolean
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(boolean)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
b
- aboolean
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, char c)
Inserts the string representation of the char
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char)
, and the character in that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
c
- achar
. - Returns:
- a reference to this object.
- Throws:
-
IndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, int i)
Inserts the string representation of the second int
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(int)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
i
- anint
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, long l)
Inserts the string representation of the long
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(long)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
l
- along
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, float f)
Inserts the string representation of the float
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(float)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
f
- afloat
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
insert
public StringBuilder insert(int offset, double d)
Inserts the string representation of the double
argument into this sequence.
The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(double)
, and the characters of that string were then inserted
into this character sequence at the indicated offset.
The offset
argument must be greater than or equal to 0
, and less than or equal to the length of this sequence.
- Parameters:
-
offset
- the offset. -
d
- adouble
. - Returns:
- a reference to this object.
- Throws:
-
StringIndexOutOfBoundsException
- if the offset is invalid.
indexOf
public int indexOf(String str)
Returns the index within this string of the first occurrence of the specified substring.
The returned index is the smallest value k
for which:
this.toString().startsWith(str, k)If no such value of
k
exists, then -1
is returned.- Parameters:
-
str
- the substring to search for. - Returns:
- the index of the first occurrence of the specified substring, or
-1
if there is no such occurrence.
indexOf
public int indexOf(String str, int fromIndex)
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
The returned index is the smallest value k
for which:
k >= Math.min(fromIndex, this.length()) && this.toString().startsWith(str, k)If no such value of
k
exists, then -1
is returned.- Parameters:
-
str
- the substring to search for. -
fromIndex
- the index from which to start the search. - Returns:
- the index of the first occurrence of the specified substring, starting at the specified index, or
-1
if there is no such occurrence.
lastIndexOf
public int lastIndexOf(String str)
Returns the index within this string of the last occurrence of the specified substring. The last occurrence of the empty string "" is considered to occur at the index value this.length()
.
The returned index is the largest value k
for which:
this.toString().startsWith(str, k)If no such value of
k
exists, then -1
is returned.- Parameters:
-
str
- the substring to search for. - Returns:
- the index of the last occurrence of the specified substring, or
-1
if there is no such occurrence.
lastIndexOf
public int lastIndexOf(String str, int fromIndex)
Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index.
The returned index is the largest value k
for which:
k <= Math.min(fromIndex, this.length()) && this.toString().startsWith(str, k)If no such value of
k
exists, then -1
is returned.- Parameters:
-
str
- the substring to search for. -
fromIndex
- the index to start the search from. - Returns:
- the index of the last occurrence of the specified substring, searching backward from the specified index, or
-1
if there is no such occurrence.
reverse
public StringBuilder reverse()
Causes this character sequence to be replaced by the reverse of the sequence. If there are any surrogate pairs included in the sequence, these are treated as single characters for the reverse operation. Thus, the order of the high-low surrogates is never reversed. Let n be the character length of this character sequence (not the length in char
values) just prior to execution of the reverse
method. Then the character at index k in the new character sequence is equal to the character at index n-k-1 in the old character sequence.
Note that the reverse operation may result in producing surrogate pairs that were unpaired low-surrogates and high-surrogates before the operation. For example, reversing "\uDC00\uD800" produces "\uD800\uDC00" which is a valid surrogate pair.
- Returns:
- a reference to this object.
length
public int length()
Returns the length (character count).
- Specified by:
-
length
in interfaceCharSequence
- Returns:
- the length of the sequence of characters currently represented by this object
capacity
public int capacity()
Returns the current capacity. The capacity is the amount of storage available for newly inserted characters, beyond which an allocation will occur.
- Returns:
- the current capacity
ensureCapacity
public void ensureCapacity(int minimumCapacity)
Ensures that the capacity is at least equal to the specified minimum. If the current capacity is less than the argument, then a new internal array is allocated with greater capacity. The new capacity is the larger of:
- The
minimumCapacity
argument. - Twice the old capacity, plus
2
.
minimumCapacity
argument is nonpositive, this method takes no action and simply returns. Note that subsequent operations on this object can reduce the actual capacity below that requested here. - Parameters:
-
minimumCapacity
- the minimum desired capacity.
trimToSize
public void trimToSize()
Attempts to reduce storage used for the character sequence. If the buffer is larger than necessary to hold its current sequence of characters, then it may be resized to become more space efficient. Calling this method may, but is not required to, affect the value returned by a subsequent call to the capacity()
method.
setLength
public void setLength(int newLength)
Sets the length of the character sequence. The sequence is changed to a new character sequence whose length is specified by the argument. For every nonnegative index k less than newLength
, the character at index k in the new character sequence is the same as the character at index k in the old sequence if k is less than the length of the old character sequence; otherwise, it is the null character '\u0000'
. In other words, if the newLength
argument is less than the current length, the length is changed to the specified length.
If the newLength
argument is greater than or equal to the current length, sufficient null characters ('\u0000'
) are appended so that length becomes the newLength
argument.
The newLength
argument must be greater than or equal to 0
.
- Parameters:
-
newLength
- the new length - Throws:
-
IndexOutOfBoundsException
- if thenewLength
argument is negative.
charAt
public char charAt(int index)
Returns the char
value in this sequence at the specified index. The first char
value is at index 0
, the next at index 1
, and so on, as in array indexing.
The index argument must be greater than or equal to 0
, and less than the length of this sequence.
If the char
value specified by the index is a surrogate, the surrogate value is returned.
- Specified by:
-
charAt
in interfaceCharSequence
- Parameters:
-
index
- the index of the desiredchar
value. - Returns:
- the
char
value at the specified index. - Throws:
-
IndexOutOfBoundsException
- ifindex
is negative or greater than or equal tolength()
.
codePointAt
public int codePointAt(int index)
Returns the character (Unicode code point) at the specified index. The index refers to char
values (Unicode code units) and ranges from 0
to CharSequence.length()
- 1
.
If the char
value specified at the given index is in the high-surrogate range, the following index is less than the length of this sequence, and the char
value at the following index is in the low-surrogate range, then the supplementary code point corresponding to this surrogate pair is returned. Otherwise, the char
value at the given index is returned.
- Parameters:
-
index
- the index to thechar
values - Returns:
- the code point value of the character at the
index
- Throws:
-
IndexOutOfBoundsException
- if theindex
argument is negative or not less than the length of this sequence.
codePointBefore
public int codePointBefore(int index)
Returns the character (Unicode code point) before the specified index. The index refers to char
values (Unicode code units) and ranges from 1
to CharSequence.length()
.
If the char
value at (index - 1)
is in the low-surrogate range, (index - 2)
is not negative, and the char
value at (index -
2)
is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If the char
value at index -
1
is an unpaired low-surrogate or a high-surrogate, the surrogate value is returned.
- Parameters:
-
index
- the index following the code point that should be returned - Returns:
- the Unicode code point value before the given index.
- Throws:
-
IndexOutOfBoundsException
- if theindex
argument is less than 1 or greater than the length of this sequence.
codePointCount
public int codePointCount(int beginIndex, int endIndex)
Returns the number of Unicode code points in the specified text range of this sequence. The text range begins at the specified beginIndex
and extends to the char
at index endIndex - 1
. Thus the length (in char
s) of the text range is endIndex-beginIndex
. Unpaired surrogates within this sequence count as one code point each.
- Parameters:
-
beginIndex
- the index to the firstchar
of the text range. -
endIndex
- the index after the lastchar
of the text range. - Returns:
- the number of Unicode code points in the specified text range
- Throws:
-
IndexOutOfBoundsException
- if thebeginIndex
is negative, orendIndex
is larger than the length of this sequence, orbeginIndex
is larger thanendIndex
.
offsetByCodePoints
public int offsetByCodePoints(int index, int codePointOffset)
Returns the index within this sequence that is offset from the given index
by codePointOffset
code points. Unpaired surrogates within the text range given by index
and codePointOffset
count as one code point each.
- Parameters:
-
index
- the index to be offset -
codePointOffset
- the offset in code points - Returns:
- the index within this sequence
- Throws:
-
IndexOutOfBoundsException
- ifindex
is negative or larger then the length of this sequence, or ifcodePointOffset
is positive and the subsequence starting withindex
has fewer thancodePointOffset
code points, or ifcodePointOffset
is negative and the subsequence beforeindex
has fewer than the absolute value ofcodePointOffset
code points.
getChars
public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
Characters are copied from this sequence into the destination character array dst
. The first character to be copied is at index srcBegin
; the last character to be copied is at index srcEnd-1
. The total number of characters to be copied is srcEnd-srcBegin
. The characters are copied into the subarray of dst
starting at index dstBegin
and ending at index:
dstbegin + (srcEnd-srcBegin) - 1
- Parameters:
-
srcBegin
- start copying at this offset. -
srcEnd
- stop copying at this offset. -
dst
- the array to copy the data into. -
dstBegin
- offset intodst
. - Throws:
-
IndexOutOfBoundsException
- if any of the following is true:-
srcBegin
is negative -
dstBegin
is negative - the
srcBegin
argument is greater than thesrcEnd
argument. -
srcEnd
is greater thanthis.length()
. -
dstBegin+srcEnd-srcBegin
is greater thandst.length
-
setCharAt
public void setCharAt(int index, char ch)
The character at the specified index is set to ch
. This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the character ch
at position index
.
The index argument must be greater than or equal to 0
, and less than the length of this sequence.
- Parameters:
-
index
- the index of the character to modify. -
ch
- the new character. - Throws:
-
IndexOutOfBoundsException
- ifindex
is negative or greater than or equal tolength()
.
substring
public String substring(int start)
Returns a new String
that contains a subsequence of characters currently contained in this character sequence. The substring begins at the specified index and extends to the end of this sequence.
- Parameters:
-
start
- The beginning index, inclusive. - Returns:
- The new string.
- Throws:
-
StringIndexOutOfBoundsException
- ifstart
is less than zero, or greater than the length of this object.
subSequence
public CharSequence subSequence(int start, int end)
Returns a new character sequence that is a subsequence of this sequence.
An invocation of this method of the form
sb.subSequence(begin, end)behaves in exactly the same way as the invocation
sb.substring(begin, end)This method is provided so that this class can implement the
CharSequence
interface.- Specified by:
-
subSequence
in interfaceCharSequence
- Parameters:
-
start
- the start index, inclusive. -
end
- the end index, exclusive. - Returns:
- the specified subsequence.
- Throws:
-
IndexOutOfBoundsException
- ifstart
orend
are negative, ifend
is greater thanlength()
, or ifstart
is greater thanend
substring
public String substring(int start, int end)
Returns a new String
that contains a subsequence of characters currently contained in this sequence. The substring begins at the specified start
and extends to the character at index end - 1
.
- Parameters:
-
start
- The beginning index, inclusive. -
end
- The ending index, exclusive. - Returns:
- The new string.
- Throws:
-
StringIndexOutOfBoundsException
- ifstart
orend
are negative or greater thanlength()
, orstart
is greater thanend
.
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.
- Specified by:
-
chars
in interfaceCharSequence
- Returns:
- an IntStream of char values from this sequence
- Since:
- 9
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.
- Specified by:
-
codePoints
in interfaceCharSequence
- Returns:
- an IntStream of Unicode code points from this sequence
- Since:
- 9