Android APIs
public final class

StringBuilder

extends Object
implements Appendable CharSequence Serializable
java.lang.Object
   ↳ java.lang.StringBuilder

Class Overview

A modifiable sequence of characters for use in creating strings. This class is intended as a direct replacement of StringBuffer for non-concurrent use; unlike StringBuffer this class is not synchronized.

For particularly complex string-building needs, consider Formatter.

The majority of the modification methods on this class return this so that method calls can be chained together. For example: new StringBuilder("a").append("b").append("c").toString().

See Also

Summary

Public Constructors
StringBuilder()
Constructs an instance with an initial capacity of 16.
StringBuilder(int capacity)
Constructs an instance with the specified capacity.
StringBuilder(CharSequence seq)
Constructs an instance that's initialized with the contents of the specified CharSequence.
StringBuilder(String str)
Constructs an instance that's initialized with the contents of the specified String.
Public Methods
StringBuilder append(char[] str, int offset, int len)
Appends the string representation of the specified subset of the char[].
StringBuilder append(double d)
Appends the string representation of the specified double value.
StringBuilder append(char c)
Appends the string representation of the specified char value.
StringBuilder append(boolean b)
Appends the string representation of the specified boolean value.
StringBuilder append(long l)
Appends the string representation of the specified long value.
StringBuilder append(float f)
Appends the string representation of the specified float value.
StringBuilder append(char[] chars)
Appends the string representation of the specified char[].
StringBuilder append(int i)
Appends the string representation of the specified int value.
StringBuilder append(String str)
Appends the contents of the specified string.
StringBuilder append(CharSequence csq, int start, int end)
Appends the string representation of the specified subsequence of the CharSequence.
StringBuilder append(StringBuffer sb)
Appends the contents of the specified StringBuffer.
StringBuilder append(Object obj)
Appends the string representation of the specified Object.
StringBuilder append(CharSequence csq)
Appends the string representation of the specified CharSequence.
StringBuilder appendCodePoint(int codePoint)
Appends the encoded Unicode code point.
int capacity()
Returns the number of characters that can be held without growing.
char charAt(int index)
Returns the character at index.
int codePointAt(int index)
Retrieves the Unicode code point value at the index.
int codePointBefore(int index)
Retrieves the Unicode code point value that precedes the index.
int codePointCount(int start, int end)
Calculates the number of Unicode code points between start and end.
StringBuilder delete(int start, int end)
Deletes a sequence of characters specified by start and end.
StringBuilder deleteCharAt(int index)
Deletes the character at the specified index.
void ensureCapacity(int min)
Ensures that this object has a minimum capacity available before requiring the internal buffer to be enlarged.
void getChars(int start, int end, char[] dst, int dstStart)
Copies the requested sequence of characters into dst passed starting at dst.
int indexOf(String subString, int start)
Searches for the index of the specified character.
int indexOf(String string)
Searches for the first index of the specified character.
StringBuilder insert(int offset, CharSequence s, int start, int end)
Inserts the string representation of the specified subsequence of the CharSequence at the specified offset.
StringBuilder insert(int offset, Object obj)
Inserts the string representation of the specified Object at the specified offset.
StringBuilder insert(int offset, float f)
Inserts the string representation of the specified float value at the specified offset.
StringBuilder insert(int offset, char c)
Inserts the string representation of the specified char value at the specified offset.
StringBuilder insert(int offset, int i)
Inserts the string representation of the specified int value at the specified offset.
StringBuilder insert(int offset, char[] ch)
Inserts the string representation of the specified char[] at the specified offset.
StringBuilder insert(int offset, double d)
Inserts the string representation of the specified double value at the specified offset.
StringBuilder insert(int offset, CharSequence s)
Inserts the string representation of the specified CharSequence at the specified offset.
StringBuilder insert(int offset, char[] str, int strOffset, int strLen)
Inserts the string representation of the specified subsequence of the char[] at the specified offset.
StringBuilder insert(int offset, String str)
Inserts the specified string at the specified offset.
StringBuilder insert(int offset, long l)
Inserts the string representation of the specified long value at the specified offset.
StringBuilder insert(int offset, boolean b)
Inserts the string representation of the specified boolean value at the specified offset.
int lastIndexOf(String subString, int start)
Searches for the index of the specified character.
int lastIndexOf(String string)
Searches for the last index of the specified character.
int length()
The current length.
int offsetByCodePoints(int index, int codePointOffset)
Returns the index that is offset codePointOffset code points from index.
StringBuilder replace(int start, int end, String string)
Replaces the specified subsequence in this builder with the specified string.
StringBuilder reverse()
Reverses the order of characters in this builder.
void setCharAt(int index, char ch)
Sets the character at the index.
void setLength(int length)
Sets the current length to a new value.
CharSequence subSequence(int start, int end)
Returns a CharSequence of the subsequence from the start index to the end index.
String substring(int start)
Returns the String value of the subsequence from the start index to the current end.
String substring(int start, int end)
Returns the String value of the subsequence from the start index to the end index.
String toString()
Returns the contents of this builder.
void trimToSize()
Trims off any extra capacity beyond the current length.
[Expand]
Inherited Methods
From class java.lang.Object
From interface java.lang.Appendable
From interface java.lang.CharSequence

Public Constructors

public StringBuilder ()

Added in API level 1

Constructs an instance with an initial capacity of 16.

See Also

public StringBuilder (int capacity)

Added in API level 1

Constructs an instance with the specified capacity.

Parameters
capacity the initial capacity to use.
Throws
NegativeArraySizeException if the specified capacity is negative.
See Also

public StringBuilder (CharSequence seq)

Added in API level 1

Constructs an instance that's initialized with the contents of the specified CharSequence. The capacity of the new builder will be the length of the CharSequence plus 16.

Parameters
seq the CharSequence to copy into the builder.
Throws
NullPointerException if seq is null.

public StringBuilder (String str)

Added in API level 1

Constructs an instance that's initialized with the contents of the specified String. The capacity of the new builder will be the length of the String plus 16.

Parameters
str the String to copy into the builder.
Throws
NullPointerException if str is null.

Public Methods

public StringBuilder append (char[] str, int offset, int len)

Added in API level 1

Appends the string representation of the specified subset of the char[]. The char[] value is converted to a String according to the rule defined by valueOf(char[], int, int).

Parameters
str the char[] to append.
offset the inclusive offset index.
len the number of characters.
Returns
  • this builder.
Throws
ArrayIndexOutOfBoundsException if offset and len do not specify a valid subsequence.
See Also

public StringBuilder append (double d)

Added in API level 1

Appends the string representation of the specified double value. The double value is converted to a string according to the rule defined by valueOf(double).

Parameters
d the double value to append.
Returns
  • this builder.
See Also

public StringBuilder append (char c)

Added in API level 1

Appends the string representation of the specified char value. The char value is converted to a string according to the rule defined by valueOf(char).

Parameters
c the char value to append.
Returns
  • this builder.
See Also

public StringBuilder append (boolean b)

Added in API level 1

Appends the string representation of the specified boolean value. The boolean value is converted to a String according to the rule defined by valueOf(boolean).

Parameters
b the boolean value to append.
Returns
  • this builder.
See Also

public StringBuilder append (long l)

Added in API level 1

Appends the string representation of the specified long value. The long value is converted to a string according to the rule defined by valueOf(long).

Parameters
l the long value.
Returns
  • this builder.
See Also

public StringBuilder append (float f)

Added in API level 1

Appends the string representation of the specified float value. The float value is converted to a string according to the rule defined by valueOf(float).

Parameters
f the float value to append.
Returns
  • this builder.
See Also

public StringBuilder append (char[] chars)

Added in API level 1

Appends the string representation of the specified char[]. The char[] is converted to a string according to the rule defined by valueOf(char[]).

Parameters
chars the char[] to append..
Returns
  • this builder.
See Also

public StringBuilder append (int i)

Added in API level 1

Appends the string representation of the specified int value. The int value is converted to a string according to the rule defined by valueOf(int).

Parameters
i the int value to append.
Returns
  • this builder.
See Also

public StringBuilder append (String str)

Added in API level 1

Appends the contents of the specified string. If the string is null, then the string "null" is appended.

Parameters
str the string to append.
Returns
  • this builder.

public StringBuilder append (CharSequence csq, int start, int end)

Added in API level 1

Appends the string representation of the specified subsequence of the CharSequence. If the CharSequence is null, then the string "null" is used to extract the subsequence from.

Parameters
csq the CharSequence to append.
start the beginning index.
end the ending index.
Returns
  • this builder.
Throws
IndexOutOfBoundsException if start or end are negative, start is greater than end or end is greater than the length of csq.

public StringBuilder append (StringBuffer sb)

Added in API level 1

Appends the contents of the specified StringBuffer. If the StringBuffer is null, then the string "null" is appended.

Parameters
sb the StringBuffer to append.
Returns
  • this builder.

public StringBuilder append (Object obj)

Added in API level 1

Appends the string representation of the specified Object. The Object value is converted to a string according to the rule defined by valueOf(Object).

Parameters
obj the Object to append.
Returns
  • this builder.
See Also

public StringBuilder append (CharSequence csq)

Added in API level 1

Appends the string representation of the specified CharSequence. If the CharSequence is null, then the string "null" is appended.

Parameters
csq the CharSequence to append.
Returns
  • this builder.

public StringBuilder appendCodePoint (int codePoint)

Added in API level 1

Appends the encoded Unicode code point. The code point is converted to a char[] as defined by toChars(int).

Parameters
codePoint the Unicode code point to encode and append.
Returns
  • this builder.
See Also

public int capacity ()

Added in API level 1

Returns the number of characters that can be held without growing.

Returns
  • the capacity
See Also

public char charAt (int index)

Added in API level 1

Returns the character at index.

Throws
IndexOutOfBoundsException if index < 0 or index >= length().

public int codePointAt (int index)

Added in API level 1

Retrieves the Unicode code point value at the index.

Parameters
index the index to the char code unit.
Returns
  • the Unicode code point value.
Throws
IndexOutOfBoundsException if index is negative or greater than or equal to length().
See Also

public int codePointBefore (int index)

Added in API level 1

Retrieves the Unicode code point value that precedes the index.

Parameters
index the index to the char code unit within this object.
Returns
  • the Unicode code point value.
Throws
IndexOutOfBoundsException if index is less than 1 or greater than length().
See Also

public int codePointCount (int start, int end)

Added in API level 1

Calculates the number of Unicode code points between start and end.

Parameters
start the inclusive beginning index of the subsequence.
end the exclusive end index of the subsequence.
Returns
  • the number of Unicode code points in the subsequence.
Throws
IndexOutOfBoundsException if start is negative or greater than end or end is greater than length().
See Also

public StringBuilder delete (int start, int end)

Added in API level 1

Deletes a sequence of characters specified by start and end. Shifts any remaining characters to the left.

Parameters
start the inclusive start index.
end the exclusive end index.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if start is less than zero, greater than the current length or greater than end.

public StringBuilder deleteCharAt (int index)

Added in API level 1

Deletes the character at the specified index. shifts any remaining characters to the left.

Parameters
index the index of the character to delete.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if index is less than zero or is greater than or equal to the current length.

public void ensureCapacity (int min)

Added in API level 1

Ensures that this object has a minimum capacity available before requiring the internal buffer to be enlarged. The general policy of this method is that if the minimumCapacity is larger than the current capacity(), then the capacity will be increased to the largest value of either the minimumCapacity or the current capacity multiplied by two plus two. Although this is the general policy, there is no guarantee that the capacity will change.

Parameters
min the new minimum capacity to set.

public void getChars (int start, int end, char[] dst, int dstStart)

Added in API level 1

Copies the requested sequence of characters into dst passed starting at dst.

Parameters
start the inclusive start index of the characters to copy.
end the exclusive end index of the characters to copy.
dst the char[] to copy the characters to.
dstStart the inclusive start index of dst to begin copying to.
Throws
IndexOutOfBoundsException if the start is negative, the dstStart is negative, the start is greater than end, the end is greater than the current length() or dstStart + end - begin is greater than dst.length.

public int indexOf (String subString, int start)

Added in API level 1

Searches for the index of the specified character. The search for the character starts at the specified offset and moves towards the end.

Parameters
subString the string to find.
start the starting offset.
Returns
  • the index of the specified character, -1 if the character isn't found
See Also

public int indexOf (String string)

Added in API level 1

Searches for the first index of the specified character. The search for the character starts at the beginning and moves towards the end.

Parameters
string the string to find.
Returns
  • the index of the specified character, -1 if the character isn't found.
See Also

public StringBuilder insert (int offset, CharSequence s, int start, int end)

Added in API level 1

Inserts the string representation of the specified subsequence of the CharSequence at the specified offset. The CharSequence is converted to a String as defined by subSequence(int, int). If the CharSequence is null, then the string "null" is used to determine the subsequence.

Parameters
offset the index to insert at.
s the CharSequence to insert.
start the start of the subsequence of the character sequence.
end the end of the subsequence of the character sequence.
Returns
  • this builder.
Throws
IndexOutOfBoundsException if offset is negative or greater than the current length(), or start and end do not specify a valid subsequence.
See Also

public StringBuilder insert (int offset, Object obj)

Added in API level 1

Inserts the string representation of the specified Object at the specified offset. The Object value is converted to a String according to the rule defined by valueOf(Object).

Parameters
offset the index to insert at.
obj the Object to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, float f)

Added in API level 1

Inserts the string representation of the specified float value at the specified offset. The float value is converted to a string according to the rule defined by valueOf(float).

Parameters
offset the index to insert at.
f the float value to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, char c)

Added in API level 1

Inserts the string representation of the specified char value at the specified offset. The char value is converted to a string according to the rule defined by valueOf(char).

Parameters
offset the index to insert at.
c the char value to insert.
Returns
  • this builder.
Throws
IndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, int i)

Added in API level 1

Inserts the string representation of the specified int value at the specified offset. The int value is converted to a String according to the rule defined by valueOf(int).

Parameters
offset the index to insert at.
i the int value to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, char[] ch)

Added in API level 1

Inserts the string representation of the specified char[] at the specified offset. The char[] value is converted to a String according to the rule defined by valueOf(char[]).

Parameters
offset the index to insert at.
ch the char[] to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, double d)

Added in API level 1

Inserts the string representation of the specified double value at the specified offset. The double value is converted to a String according to the rule defined by valueOf(double).

Parameters
offset the index to insert at.
d the double value to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, CharSequence s)

Added in API level 1

Inserts the string representation of the specified CharSequence at the specified offset. The CharSequence is converted to a String as defined by toString(). If s is null, then the String "null" is inserted.

Parameters
offset the index to insert at.
s the CharSequence to insert.
Returns
  • this builder.
Throws
IndexOutOfBoundsException if offset is negative or greater than the current length().
See Also

public StringBuilder insert (int offset, char[] str, int strOffset, int strLen)

Added in API level 1

Inserts the string representation of the specified subsequence of the char[] at the specified offset. The char[] value is converted to a String according to the rule defined by valueOf(char[], int, int).

Parameters
offset the index to insert at.
str the char[] to insert.
strOffset the inclusive index.
strLen the number of characters.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length(), or strOffset and strLen do not specify a valid subsequence.
See Also

public StringBuilder insert (int offset, String str)

Added in API level 1

Inserts the specified string at the specified offset. If the specified string is null, then the String "null" is inserted.

Parameters
offset the index to insert at.
str the String to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length().

public StringBuilder insert (int offset, long l)

Added in API level 1

Inserts the string representation of the specified long value at the specified offset. The long value is converted to a String according to the rule defined by valueOf(long).

Parameters
offset the index to insert at.
l the long value to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current {code length()}.
See Also

public StringBuilder insert (int offset, boolean b)

Added in API level 1

Inserts the string representation of the specified boolean value at the specified offset. The boolean value is converted to a string according to the rule defined by valueOf(boolean).

Parameters
offset the index to insert at.
b the boolean value to insert.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if offset is negative or greater than the current length.
See Also

public int lastIndexOf (String subString, int start)

Added in API level 1

Searches for the index of the specified character. The search for the character starts at the specified offset and moves towards the beginning.

Parameters
subString the string to find.
start the starting offset.
Returns
  • the index of the specified character, -1 if the character isn't found.
Throws
NullPointerException if subString is null.
See Also

public int lastIndexOf (String string)

Added in API level 1

Searches for the last index of the specified character. The search for the character starts at the end and moves towards the beginning.

Parameters
string the string to find.
Returns
  • the index of the specified character, -1 if the character isn't found.
Throws
NullPointerException if string is null.
See Also

public int length ()

Added in API level 1

The current length.

Returns
  • the number of characters contained in this instance.

public int offsetByCodePoints (int index, int codePointOffset)

Added in API level 1

Returns the index that is offset codePointOffset code points from index.

Parameters
index the index to calculate the offset from.
codePointOffset the number of code points to count.
Returns
  • the index that is codePointOffset code points away from index.
Throws
IndexOutOfBoundsException if index is negative or greater than length() or if there aren't enough code points before or after index to match codePointOffset.
See Also

public StringBuilder replace (int start, int end, String string)

Added in API level 1

Replaces the specified subsequence in this builder with the specified string.

Parameters
start the inclusive begin index.
end the exclusive end index.
string the replacement string.
Returns
  • this builder.
Throws
StringIndexOutOfBoundsException if start is negative, greater than the current length() or greater than end.
NullPointerException if str is null.

public StringBuilder reverse ()

Added in API level 1

Reverses the order of characters in this builder.

Returns
  • this buffer.

public void setCharAt (int index, char ch)

Added in API level 1

Sets the character at the index.

Parameters
index the zero-based index of the character to replace.
ch the character to set.
Throws
IndexOutOfBoundsException if index is negative or greater than or equal to the current length().

public void setLength (int length)

Added in API level 1

Sets the current length to a new value. If the new length is larger than the current length, then the new characters at the end of this object will contain the char value of

public void trimToSize ()

Added in API level 1

Trims off any extra capacity beyond the current length. Note, this method is NOT guaranteed to change the capacity of this object.