StringBuilder
class StringBuilder : Appendable, CharSequence, Comparable<StringBuilder!>, Serializable
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 java.lang.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.
Summary
| Public constructors |
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Constructs a string builder with no characters in it and an initial capacity of 16 characters.
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Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
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Constructs a string builder that contains the same characters as the specified CharSequence.
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Constructs a string builder initialized to the contents of the specified string.
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| Properties |
| Int |
Returns the length (character count).
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Public constructors
StringBuilder
StringBuilder()
Constructs a string builder with no characters in it and an initial capacity of 16 characters.
StringBuilder
StringBuilder(capacity: Int)
Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
| Parameters |
capacity |
Int: the initial capacity. |
| Exceptions |
java.lang.NegativeArraySizeException |
if the capacity argument is less than 0. |
StringBuilder
StringBuilder(seq: CharSequence)
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.
StringBuilder
StringBuilder(str: String)
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 |
String: the initial contents of the buffer. |
Public methods
append
fun append(c: Char): StringBuilder
| Parameters |
c |
Char: The character to append |
| Exceptions |
java.io.IOException |
If an I/O error occurs |
append
fun append(s: CharSequence?): StringBuilder
| Parameters |
csq |
The character sequence to append. If csq is null, then the four characters "null" are appended to this Appendable. |
| Exceptions |
java.io.IOException |
If an I/O error occurs |
append
fun append(
s: CharSequence?,
start: Int,
end: Int
): StringBuilder
| Parameters |
csq |
The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null". |
start |
Int: The index of the first character in the subsequence |
end |
Int: The index of the character following the last character in the subsequence |
| Exceptions |
java.lang.IndexOutOfBoundsException |
If start or end are negative, start is greater than end, or end is greater than csq.length() |
java.io.IOException |
If an I/O error occurs |
append
fun append(sb: StringBuffer?): StringBuilder
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.
capacity
fun capacity(): Int
Returns the current capacity. The capacity is the amount of storage available for newly inserted characters, beyond which an allocation will occur.
| Return |
Int |
the current capacity |
chars
fun chars(): IntStream
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.
| Return |
IntStream |
an IntStream of char values from this sequence |
codePointAt
fun codePointAt(index: Int): Int
Returns the character (Unicode code point) at the specified index. The index refers to char values (Unicode code units) and ranges from 0 to 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 |
Int: the index to the char values |
| Return |
Int |
the code point value of the character at the index |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if the index argument is negative or not less than the length of this sequence. |
codePointBefore
fun codePointBefore(index: Int): Int
Returns the character (Unicode code point) before the specified index. The index refers to char values (Unicode code units) and ranges from 1 to 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 |
Int: the index following the code point that should be returned |
| Return |
Int |
the Unicode code point value before the given index. |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if the index argument is less than 1 or greater than the length of this sequence. |
codePointCount
fun codePointCount(
beginIndex: Int,
endIndex: Int
): Int
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 chars) of the text range is endIndex-beginIndex. Unpaired surrogates within this sequence count as one code point each.
| Parameters |
beginIndex |
Int: the index to the first char of the text range. |
endIndex |
Int: the index after the last char of the text range. |
| Return |
Int |
the number of Unicode code points in the specified text range |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if the beginIndex is negative, or endIndex is larger than the length of this sequence, or beginIndex is larger than endIndex. |
codePoints
fun codePoints(): IntStream
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.
| Return |
IntStream |
an IntStream of Unicode code points from this sequence |
compareTo
fun compareTo(other: StringBuilder): Int
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 java.text.Collator.
| Parameters |
o |
the object to be compared. |
another |
the StringBuilder to be compared with |
| Return |
Int |
the value 0 if this StringBuilder contains the same character sequence as that of the argument StringBuilder; a negative integer if this StringBuilder is lexicographically less than the StringBuilder argument; or a positive integer if this StringBuilder is lexicographically greater than the StringBuilder argument. |
| Exceptions |
java.lang.NullPointerException |
if the specified object is null |
java.lang.ClassCastException |
if the specified object's type prevents it from being compared to this object. |
delete
fun delete(
start: Int,
end: Int
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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deleteCharAt
fun deleteCharAt(index: Int): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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ensureCapacity
fun ensureCapacity(minimumCapacity: Int): Unit
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.
If the
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 |
Int: the minimum desired capacity. |
get
fun get(index: Int): Char
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.
| Parameters |
index |
Int: the index of the desired char value. |
| Return |
Char |
the char value at the specified index. |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if index is negative or greater than or equal to length(). |
getChars
fun getChars(
srcBegin: Int,
srcEnd: Int,
dst: CharArray!,
dstBegin: Int
): Unit
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:
<code>dstbegin + (srcEnd-srcBegin) - 1
</code>
| Parameters |
srcBegin |
Int: start copying at this offset. |
srcEnd |
Int: stop copying at this offset. |
dst |
CharArray!: the array to copy the data into. |
dstBegin |
Int: offset into dst. |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if any of the following is true:
srcBegin is negative dstBegin is negative - the
srcBegin argument is greater than the srcEnd argument.
srcEnd is greater than this.length(). dstBegin+srcEnd-srcBegin is greater than dst.length
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insert
fun insert(
offset: Int,
c: Char
): StringBuilder
| Exceptions |
java.lang.IndexOutOfBoundsException |
|
insert
fun insert(
offset: Int,
d: Double
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
|
insert
fun insert(
offset: Int,
f: Float
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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insert
fun insert(
offset: Int,
i: Int
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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insert
fun insert(
offset: Int,
obj: Any?
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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insert
fun insert(
offset: Int,
str: String?
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
|
insert
fun insert(
offset: Int,
l: Long
): StringBuilder
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
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lastIndexOf
fun lastIndexOf(str: String): Int
lastIndexOf
fun lastIndexOf(
str: String,
fromIndex: Int
): Int
offsetByCodePoints
fun offsetByCodePoints(
index: Int,
codePointOffset: Int
): Int
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 |
Int: the index to be offset |
codePointOffset |
Int: the offset in code points |
| Return |
Int |
the index within this sequence |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if index is negative or larger then the length of this sequence, or if codePointOffset is positive and the subsequence starting with index has fewer than codePointOffset code points, or if codePointOffset is negative and the subsequence before index has fewer than the absolute value of codePointOffset code points. |
setCharAt
fun setCharAt(
index: Int,
ch: Char
): Unit
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 |
Int: the index of the character to modify. |
ch |
Char: the new character. |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if index is negative or greater than or equal to length(). |
setLength
fun setLength(newLength: Int): Unit
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 '\u005Cu0000'. 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 ('\u005Cu0000') are appended so that length becomes the newLength argument.
The newLength argument must be greater than or equal to 0.
| Parameters |
newLength |
Int: the new length |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if the newLength argument is negative. |
subSequence
fun subSequence(
startIndex: Int,
endIndex: Int
): CharSequence
Returns a new character sequence that is a subsequence of this sequence.
An invocation of this method of the form
<code>sb.subSequence(begin,&nbsp;end)</code>
behaves in exactly the same way as the invocation
<code>sb.substring(begin,&nbsp;end)</code>
This method is provided so that this class can implement the
CharSequence interface.
| Parameters |
start |
the start index, inclusive. |
end |
the end index, exclusive. |
| Exceptions |
java.lang.IndexOutOfBoundsException |
if start or end are negative, if end is greater than length(), or if start is greater than end |
substring
fun substring(start: Int): String
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 |
Int: The beginning index, inclusive. |
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
if start is less than zero, or greater than the length of this object. |
substring
fun substring(
start: Int,
end: Int
): String
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 |
Int: The beginning index, inclusive. |
end |
Int: The ending index, exclusive. |
| Exceptions |
java.lang.StringIndexOutOfBoundsException |
if start or end are negative or greater than length(), or start is greater than end. |
toString
fun toString(): String
| Return |
String |
a string consisting of exactly this sequence of characters |
trimToSize
fun trimToSize(): Unit
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.
Properties
length
val length: Int
Returns the length (character count).
| Return |
Int |
the length of the sequence of characters currently represented by this object |
