java.lang
Class StringBuilder

java.lang.Object
  extended by java.lang.StringBuilder

@TransactionType(value=SUPPORTS)
public final class StringBuilder
extends Object

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.

This Java Card class is a subset of the JDK 1.5 StringBuilder class. Some interfaces, methods and/or variables have been pruned, and/or other methods simplified, in an effort to reduce the size of this class and/or eliminate dependencies on unsupported features.

Since:
JDK 1.5, Java Card 3.0
See Also:
StringBuffer, String

Constructor Summary
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 capacity argument.
StringBuilder(String str)
          Constructs a string builder initialized to the contents of the specified string.
 
Method Summary
 StringBuilder append(boolean b)
          Appends the string representation of the boolean argument to the sequence.
 StringBuilder append(char c)
          Appends the string representation of the char argument to this sequence.
 StringBuilder append(char[] str)
          Appends the string representation of the char array argument to this sequence.
 StringBuilder append(char[] str, int offset, int len)
          Appends the string representation of a subarray of the char array argument to this sequence.
 StringBuilder append(int i)
          Appends the string representation of the int argument to this sequence.
 StringBuilder append(long l)
          Appends the string representation of the long argument to this sequence.
 StringBuilder append(Object obj)
           
 StringBuilder append(String str)
          Appends the specified string to this character sequence.
 StringBuilder append(StringBuffer sb)
          Appends the specified StringBuffer to this sequence.
 int capacity()
          Returns the current capacity.
 char charAt(int index)
          Returns the char value in this sequence at the specified index.
 StringBuilder delete(int start, int end)
          Removes the characters in a substring of this sequence.
 StringBuilder deleteCharAt(int index)
          Removes the char at the specified position in this sequence.
 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 dst.
 StringBuilder insert(int offset, boolean b)
          Inserts the string representation of the boolean argument into this sequence.
 StringBuilder insert(int offset, char c)
          Inserts the string representation of the char argument into this sequence.
 StringBuilder insert(int offset, char[] str)
          Inserts the string representation of the char array argument into this sequence.
 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.
 StringBuilder insert(int offset, int i)
          Inserts the string representation of the second int argument into this sequence.
 StringBuilder insert(int offset, long l)
          Inserts the string representation of the long argument into this sequence.
 StringBuilder insert(int offset, Object obj)
          Inserts the string representation of the Object argument into this character sequence.
 StringBuilder insert(int offset, String str)
          Inserts the string into this character sequence.
 int length()
          Returns the length (character count).
 StringBuilder replace(int start, int end, String str)
          Replaces the characters in a substring of this sequence with characters in the specified String.
 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 ch.
 void setLength(int newLength)
          Sets the length of the character sequence.
 String toString()
          Returns a string representing the data in this sequence.
 void trimToSize()
          Attempts to reduce storage used for the character sequence.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

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 the capacity argument is less than 0.

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.
Throws:
NullPointerException - if str is null
Method Detail

length

public int length()
Returns the length (character count).

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: If the minimumCapacity argument is nonpositive, this method takes no action and simply returns.

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 the newLength 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.

Parameters:
index - the index of the desired char value.
Returns:
the char value at the specified index.
Throws:
IndexOutOfBoundsException - if index is negative or greater than or equal to length().

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 into dst.
Throws:
NullPointerException - if dst is null.
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

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 - if index is negative or greater than or equal to length().

append

public StringBuilder append(Object obj)
See Also:
String.valueOf(java.lang.Object), append(java.lang.String)

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 - the StringBuffer to append.
Returns:
a reference to this object.

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 first char to append.
len - the number of chars to append.
Returns:
a reference to this object.

append

public StringBuilder append(boolean b)
Appends the string representation of the boolean argument to the sequence.

The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.

Parameters:
b - a boolean.
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.

Parameters:
c - a char.
Returns:
a reference to this object.

append

public StringBuilder append(int i)
Appends the string representation of the int argument to this sequence.

The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.

Parameters:
i - an int.
Returns:
a reference to this object.

append

public StringBuilder append(long l)
Appends the string representation of the long argument to this sequence.

The argument is converted to a string as if by the method String.valueOf, and the characters of that string are then appended to this sequence.

Parameters:
l - a long.
Returns:
a reference to this object.

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 - if start is negative, greater than length(), or greater than end.

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 chars to remove by calling Character.charCount(thisSequence.codePointAt(index)), where thisSequence is this sequence.

Parameters:
index - Index of char to remove
Returns:
This object.
Throws:
StringIndexOutOfBoundsException - if the index is negative or greater than or equal to length().

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 - if start is negative, greater than length(), or greater than end.

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 chars. The characters of the subarray are inserted into this sequence at the position indicated by index. The length of this sequence increases by len chars.

Parameters:
index - position at which to insert subarray.
str - A char array.
offset - the index of the first char in subarray to be inserted.
len - the number of chars in the subarray to be inserted.
Returns:
This object
Throws:
StringIndexOutOfBoundsException - if index is negative or greater than length(), or offset or len are negative, or (offset+len) is greater than str.length.

insert

public StringBuilder insert(int offset,
                            Object obj)
Inserts the string representation of the Object argument into this character sequence.

The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this 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 - an Object.
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 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 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 position indicated by offset.

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 offset,
                            boolean b)
Inserts the string representation of the boolean argument into this sequence.

The second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this 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 - a boolean.
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 second argument is inserted into the contents of this sequence at the position indicated by offset. The length of this sequence increases by one.

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 inserted into this character sequence at the position indicated by 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 - a char.
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 second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this 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 - an int.
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 second argument is converted to a string as if by the method String.valueOf, and the characters of that string are then inserted into this sequence at the position indicated by 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 - a long.
Returns:
a reference to this object.
Throws:
StringIndexOutOfBoundsException - if the offset is invalid.

reverse

public StringBuilder reverse()
Causes this character sequence to be replaced by the reverse of the sequence. 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.

Returns:
a reference to this object.

toString

public String toString()
Returns a string representing the data in this sequence. A new String object is allocated and initialized to contain the character sequence currently represented by this object. This String is then returned. Subsequent changes to this sequence do not affect the contents of the String.

Overrides:
toString in class Object
Returns:
a string representation of this sequence of characters.


Copyright (c) 2009 Sun Microsystems, Inc. All rights reserved.