Class StringBuffer

java.lang.Object
java.lang.StringBuffer
All Implemented Interfaces:
Serializable,Appendable,CharSequence,Comparable<StringBuffer>
public final classStringBufferextendsObjectimplementsAppendable,Serializable,Comparable<StringBuffer>,CharSequence
A thread-safe, mutable sequence of characters. A string buffer is like aString, but can be modified. At any point in time it contains some particular sequence of characters, but the length and content of the sequence can be changed through certain method calls.

String buffers are safe for use by multiple threads. The methods are synchronized where necessary so that all the operations on any particular instance behave as if they occur in some serial order that is consistent with the order of the method calls made by each of the individual threads involved.

The principal operations on aStringBuffer are theappend andinsert 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 buffer. Theappend method always adds these characters at the end of the buffer; theinsert method adds the characters at a specified point.

For example, ifz refers to a string buffer object whose current contents are"start", then the method callz.append("le") would cause the string buffer to contain"startle", whereasz.insert(4, "le") would alter the string buffer to contain"starlet".

In general, if sb refers to an instance of aStringBuffer, thensb.append(x) has the same effect assb.insert(sb.length(), x).

Whenever an operation occurs involving a source sequence (such as appending or inserting from a source sequence), this class synchronizes only on the string buffer performing the operation, not on the source. Note that whileStringBuffer is designed to be safe to use concurrently from multiple threads, if the constructor or theappend orinsert operation is passed a source sequence that is shared across threads, the calling code must ensure that the operation has a consistent and unchanging view of the source sequence for the duration of the operation. This could be satisfied by the caller holding a lock during the operation's call, by using an immutable source sequence, or by not sharing the source sequence across threads.

Every string buffer has a capacity. As long as the length of the character sequence contained in the string buffer does not exceed the capacity, it is not necessary to allocate a new internal buffer array. If the internal buffer overflows, it is automatically made larger.

Unless otherwise noted, passing anull argument to a constructor or method in this class will cause aNullPointerException to be thrown.

As of release JDK 5, this class has been supplemented with an equivalent class designed for use by a single thread,StringBuilder. TheStringBuilder class should generally be used in preference to this one, as it supports all of the same operations but it is faster, as it performs no synchronization.

API Note:
StringBuffer implementsComparable but does not overrideequals. Thus, the natural ordering ofStringBuffer is inconsistent with equals. Care should be exercised ifStringBuffer objects are used as keys in aSortedMap or elements in aSortedSet. SeeComparable,SortedMap, orSortedSet for more information.
Since:
1.0
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    Constructs a string buffer with no characters in it and an initial capacity of 16 characters.
    StringBuffer(int capacity)
    Constructs a string buffer with no characters in it and the specified initial capacity.
    Constructs a string buffer that contains the same characters as the specifiedCharSequence.
    Constructs a string buffer initialized to the contents of the specified string.

  • Method Summary

    Modifier and Type
    Method
    Description
    append(boolean b)
    Appends the string representation of theboolean argument to the sequence.
    append(char c)
    Appends the string representation of thechar argument to this sequence.
    append(char[] str)
    Appends the string representation of thechar array argument to this sequence.
    append(char[] str, int offset, int len)
    Appends the string representation of a subarray of thechar array argument to this sequence.
    append(double d)
    Appends the string representation of thedouble argument to this sequence.
    append(float f)
    Appends the string representation of thefloat argument to this sequence.
    append(int i)
    Appends the string representation of theint argument to this sequence.
    append(long lng)
    Appends the string representation of thelong argument to this sequence.
    Appends the specifiedCharSequence to this sequence.
    append(CharSequence s, int start, int end)
    Appends a subsequence of the specifiedCharSequence to this sequence.
    Appends the string representation of theObject argument.
    Appends the specified string to this character sequence.
    Appends the specifiedStringBuffer to this sequence.
    appendCodePoint(int codePoint)
    Appends the string representation of thecodePoint argument to this sequence.
    int
    Returns the current capacity.
    char
    charAt(int index)
    Returns thechar value in this sequence at the specified index.
    Returns a stream ofint zero-extending thechar values from this sequence.
    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.
    Returns a stream of code point values from this sequence.
    int
    Compares twoStringBuffer instances lexicographically.
    delete(int start, int end)
    Removes the characters in a substring of this sequence.
    deleteCharAt(int index)
    Removes thechar 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 arraydst.
    int
    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.
    insert(int offset, boolean b)
    Inserts the string representation of theboolean argument into this sequence.
    insert(int offset, char c)
    Inserts the string representation of thechar argument into this sequence.
    insert(int offset, char[] str)
    Inserts the string representation of thechar array argument into this sequence.
    insert(int index, char[] str, int offset, int len)
    Inserts the string representation of a subarray of thestr array argument into this sequence.
    insert(int offset, double d)
    Inserts the string representation of thedouble argument into this sequence.
    insert(int offset, float f)
    Inserts the string representation of thefloat argument into this sequence.
    insert(int offset, int i)
    Inserts the string representation of the secondint argument into this sequence.
    insert(int offset, long l)
    Inserts the string representation of thelong argument into this sequence.
    insert(int dstOffset,CharSequence s)
    Inserts the specifiedCharSequence into this sequence.
    insert(int dstOffset,CharSequence s, int start, int end)
    Inserts a subsequence of the specifiedCharSequence into this sequence.
    insert(int offset,Object obj)
    Inserts the string representation of theObject argument into this character sequence.
    insert(int offset,String str)
    Inserts the string into this character sequence.
    int
    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
    Returns the length (character count).
    int
    offsetByCodePoints(int index, int codePointOffset)
    Returns the index within this sequence that is offset from the givenindex bycodePointOffset code points.
    repeat(int codePoint, int count)
    Repeatscount copies of the string representation of thecodePoint argument to this sequence.
    repeat(CharSequence cs, int count)
    Appendscount copies of the specifiedCharSequencecs to this sequence.
    replace(int start, int end,String str)
    Replaces the characters in a substring of this sequence with characters in the specifiedString.
    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 toch.
    void
    setLength(int newLength)
    Sets the length of the character sequence.
    subSequence(int start, int end)
    Returns a new character sequence that is a subsequence of this sequence.
    substring(int start)
    Returns a newString that contains a subsequence of characters currently contained in this character sequence.
    substring(int start, int end)
    Returns a newString that contains a subsequence of characters currently contained in this sequence.
    Returns a string representing the data in this sequence.
    void
    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

    chars,codePoints,isEmpty

  • Constructor Details

    • StringBuffer

      public StringBuffer()
      Constructs a string buffer with no characters in it and an initial capacity of 16 characters.

    • StringBuffer

      public StringBuffer(int capacity)
      Constructs a string buffer with no characters in it and the specified initial capacity.
      Parameters:
      capacity - the initial capacity.
      Throws:
      NegativeArraySizeException - if thecapacity argument is less than0.

    • StringBuffer

      public StringBuffer(String str)
      Constructs a string buffer initialized to the contents of the specified string. The initial capacity of the string buffer is16 plus the length of the string argument.
      Parameters:
      str - the initial contents of the buffer.

    • StringBuffer

      public StringBuffer(CharSequence seq)
      Constructs a string buffer that contains the same characters as the specifiedCharSequence. The initial capacity of the string buffer is16 plus the length of theCharSequence argument.
      Parameters:
      seq - the sequence to copy.
      Since:
      1.5

  • Method Details

    • compareTo

      public int compareTo(StringBuffer another)
      Compares twoStringBuffer instances lexicographically. This method follows the same rules for lexicographical comparison as defined in theCharSequence.compare(this, another) method.

      For finer-grained, locale-sensitive String comparison, refer toCollator.

      Specified by:
      compareTo in interface Comparable<StringBuffer>
      Implementation Note:
      This method synchronizes onthis, the current object, but notStringBuffer another with whichthis StringBuffer is compared.
      Parameters:
      another - theStringBuffer to be compared with
      Returns:
      the value0 if thisStringBuffer contains the same character sequence as that of the argumentStringBuffer; a negative integer if thisStringBuffer is lexicographically less than theStringBuffer argument; or a positive integer if thisStringBuffer is lexicographically greater than theStringBuffer argument.
      Since:
      11

    • length

      public int length()
      Returns the length (character count).
      Specified by:
      length in interface CharSequence
      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 number of characters that can be stored (including already written 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:
      • TheminimumCapacity argument.
      • Twice the old capacity, plus2.
      If theminimumCapacity 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 thecapacity() method.
      Since:
      1.5

    • 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 indexk less thannewLength, the character at indexk in the new character sequence is the same as the character at indexk in the old sequence ifk is less than the length of the old character sequence; otherwise, it is the null character'\u0000'. In other words, if thenewLength argument is less than the current length, the length is changed to the specified length.

      If thenewLength argument is greater than or equal to the current length, sufficient null characters ('\u0000') are appended so that length becomes thenewLength argument.

      ThenewLength argument must be greater than or equal to0.

      Parameters:
      newLength - the new length
      Throws:
      IndexOutOfBoundsException - if thenewLength argument is negative.
      See Also:

    • charAt

      public char charAt(int index)
      Returns thechar value in this sequence at the specified index. The firstchar value is at index0, the next at index1, and so on, as in array indexing.

      The index argument must be greater than or equal to0, and less than the length of this sequence.

      If thechar value specified by the index is asurrogate, the surrogate value is returned.

      Specified by:
      charAt in interface CharSequence
      Parameters:
      index - the index of the desiredchar value.
      Returns:
      thechar value at the specified index.
      Throws:
      IndexOutOfBoundsException - ifindex is negative or greater than or equal tolength().
      See Also:

    • codePointAt

      public int codePointAt(int index)
      Returns the character (Unicode code point) at the specified index. The index refers tochar values (Unicode code units) and ranges from0 toCharSequence.length() - 1.

      If thechar value specified at the given index is in the high-surrogate range, the following index is less than the length of this sequence, and thechar value at the following index is in the low-surrogate range, then the supplementary code point corresponding to this surrogate pair is returned. Otherwise, thechar value at the given index is returned.

      Parameters:
      index - the index to thechar values
      Returns:
      the code point value of the character at theindex
      Throws:
      IndexOutOfBoundsException - if theindex argument is negative or not less than the length of this sequence.
      Since:
      1.5

    • codePointBefore

      public int codePointBefore(int index)
      Returns the character (Unicode code point) before the specified index. The index refers tochar values (Unicode code units) and ranges from1 toCharSequence.length().

      If thechar value at(index - 1) is in the low-surrogate range,(index - 2) is not negative, and thechar value at(index - 2) is in the high-surrogate range, then the supplementary code point value of the surrogate pair is returned. If thechar value atindex - 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.
      Since:
      1.5

    • 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 specifiedbeginIndex and extends to thechar at indexendIndex - 1. Thus the length (inchars) of the text range isendIndex-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.
      Since:
      1.5

    • offsetByCodePoints

      public int offsetByCodePoints(int index, int codePointOffset)
      Returns the index within this sequence that is offset from the givenindex bycodePointOffset code points. Unpaired surrogates within the text range given byindex andcodePointOffset 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 than 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.
      Since:
      1.5

    • getChars

      public void getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
      Characters are copied from this sequence into the destination character arraydst. The first character to be copied is at indexsrcBegin; the last character to be copied is at indexsrcEnd-1. The total number of characters to be copied issrcEnd-srcBegin. The characters are copied into the subarray ofdst starting at indexdstBegin 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
      • thesrcBegin 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 toch. This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the characterch at positionindex.

      The index argument must be greater than or equal to0, 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().
      See Also:

    • append

      public StringBuffer append(Object obj)
      Appends the string representation of theObject argument.

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(Object), and the characters of that string were thenappended to this character sequence.

      Parameters:
      obj - anObject.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(String str)
      Appends the specified string to this character sequence.

      The characters of theString argument are appended, in order, increasing the length of this sequence by the length of the argument. Ifstr isnull, then the four characters"null" are appended.

      Letn be the length of this character sequence just prior to execution of theappend method. Then the character at indexk in the new character sequence is equal to the character at indexk in the old character sequence, ifk is less thann; otherwise, it is equal to the character at indexk-n in the argumentstr.

      Parameters:
      str - a string.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(StringBuffer sb)
      Appends the specifiedStringBuffer to this sequence.

      The characters of theStringBuffer argument are appended, in order, to the contents of thisStringBuffer, increasing the length of thisStringBuffer by the length of the argument. Ifsb isnull, then the four characters"null" are appended to thisStringBuffer.

      Letn be the length of the old character sequence, the one contained in theStringBuffer just prior to execution of theappend method. Then the character at indexk in the new character sequence is equal to the character at indexk in the old character sequence, ifk is less thann; otherwise, it is equal to the character at indexk-n in the argumentsb.

      This method synchronizes onthis, the destination object, but does not synchronize on the source (sb).

      Parameters:
      sb - theStringBuffer to append.
      Returns:
      a reference to this object.
      Since:
      1.4

    • append

      public StringBuffer append(CharSequence s)
      Appends the specifiedCharSequence to this sequence.

      The characters of theCharSequence argument are appended, in order, increasing the length of this sequence by the length of the argument.

      The result of this method is exactly the same as if it were an invocation of this.append(s, 0, s.length());

      This method synchronizes onthis, the destination object, but does not synchronize on the source (s).

      Ifs isnull, then the four characters"null" are appended.

      Specified by:
      append in interface Appendable
      Parameters:
      s - theCharSequence to append.
      Returns:
      a reference to this object.
      Since:
      1.5

    • append

      public StringBuffer append(CharSequence s, int start, int end)
      Appends a subsequence of the specifiedCharSequence to this sequence.

      Characters of the arguments, starting at indexstart, are appended, in order, to the contents of this sequence up to the (exclusive) indexend. The length of this sequence is increased by the value ofend - start.

      Letn be the length of this character sequence just prior to execution of theappend method. Then the character at indexk in this character sequence becomes equal to the character at indexk in this sequence, ifk is less thann; otherwise, it is equal to the character at indexk+start-n in the arguments.

      Ifs isnull, then this method appends characters as if the s parameter was a sequence containing the four characters"null".

      The contents are unspecified if theCharSequence is modified during the method call or an exception is thrown when accessing theCharSequence.

      Specified by:
      append in interface Appendable
      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()
      Since:
      1.5

    • append

      public StringBuffer append(char[] str)
      Appends the string representation of thechar 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 methodString.valueOf(char[]), and the characters of that string were thenappended to this character sequence.

      Parameters:
      str - the characters to be appended.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(char[] str, int offset, int len)
      Appends the string representation of a subarray of thechar array argument to this sequence.

      Characters of thechar arraystr, starting at indexoffset, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value oflen.

      The overall effect is exactly as if the arguments were converted to a string by the methodString.valueOf(char[],int,int), and the characters of that string were thenappended to this character sequence.

      Parameters:
      str - the characters to be appended.
      offset - the index of the firstchar to append.
      len - the number ofchars to append.
      Returns:
      a reference to this object.
      Throws:
      IndexOutOfBoundsException - ifoffset < 0 orlen < 0 oroffset+len > str.length

    • append

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

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(boolean), and the characters of that string were thenappended to this character sequence.

      Parameters:
      b - aboolean.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(char c)
      Appends the string representation of thechar argument to this sequence.

      The argument is appended to the contents of this sequence. The length of this sequence increases by1.

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(char), and the character in that string were thenappended to this character sequence.

      Specified by:
      append in interface Appendable
      Parameters:
      c - achar.
      Returns:
      a reference to this object.

    • append

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

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(int), and the characters of that string were thenappended to this character sequence.

      Parameters:
      i - anint.
      Returns:
      a reference to this object.

    • appendCodePoint

      public StringBuffer appendCodePoint(int codePoint)
      Appends the string representation of thecodePoint argument to this sequence.

      The argument is appended to the contents of this sequence. The length of this sequence increases byCharacter.charCount(codePoint).

      The overall effect is exactly as if the argument were converted to achar array by the methodCharacter.toChars(int) and the character in that array were thenappended to this character sequence.

      Parameters:
      codePoint - a Unicode code point
      Returns:
      a reference to this object.
      Since:
      1.5

    • append

      public StringBuffer append(long lng)
      Appends the string representation of thelong argument to this sequence.

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(long), and the characters of that string were thenappended to this character sequence.

      Parameters:
      lng - along.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(float f)
      Appends the string representation of thefloat argument to this sequence.

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(float), and the characters of that string were thenappended to this character sequence.

      Parameters:
      f - afloat.
      Returns:
      a reference to this object.

    • append

      public StringBuffer append(double d)
      Appends the string representation of thedouble argument to this sequence.

      The overall effect is exactly as if the argument were converted to a string by the methodString.valueOf(double), and the characters of that string were thenappended to this character sequence.

      Parameters:
      d - adouble.
      Returns:
      a reference to this object.

    • delete

      public StringBuffer delete(int start, int end)
      Removes the characters in a substring of this sequence. The substring begins at the specifiedstart and extends to the character at indexend - 1 or to the end of the sequence if no such character exists. Ifstart is equal toend, 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.
      Since:
      1.2

    • deleteCharAt

      public StringBuffer deleteCharAt(int index)
      Removes thechar at the specified position in this sequence. This sequence is shortened by onechar.

      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 ofchars to remove by callingCharacter.charCount(thisSequence.codePointAt(index)), wherethisSequence is this sequence.

      Parameters:
      index - Index ofchar to remove
      Returns:
      This object.
      Throws:
      StringIndexOutOfBoundsException - if theindex is negative or greater than or equal tolength().
      Since:
      1.2

    • replace

      public StringBuffer replace(int start, int end,String str)
      Replaces the characters in a substring of this sequence with characters in the specifiedString. The substring begins at the specifiedstart and extends to the character at indexend - 1 or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specifiedString is inserted atstart. (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.
      Since:
      1.2

    • substring

      public String substring(int start)
      Returns a newString 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.
      Since:
      1.2

    • 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 theCharSequence interface.

      Specified by:
      subSequence in interface CharSequence
      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
      Since:
      1.4

    • substring

      public String substring(int start, int end)
      Returns a newString that contains a subsequence of characters currently contained in this sequence. The substring begins at the specifiedstart and extends to the character at indexend - 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.
      Since:
      1.2

    • insert

      public StringBuffer insert(int index, char[] str, int offset, int len)
      Inserts the string representation of a subarray of thestr array argument into this sequence. The subarray begins at the specifiedoffset and extendslenchars. The characters of the subarray are inserted into this sequence at the position indicated byindex. The length of this sequence increases bylenchars.
      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 ofchars 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.
      Since:
      1.2

    • insert

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

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(Object), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      obj - anObject.
      Returns:
      a reference to this object.
      Throws:
      StringIndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset,String str)
      Inserts the string into this character sequence.

      The characters of theString 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. Ifstr isnull, then the four characters"null" are inserted into this sequence.

      The character at indexk in the new character sequence is equal to:

      • the character at indexk in the old character sequence, ifk is less thanoffset
      • the character at indexk-offset in the argumentstr, ifk is not less thanoffset but is less thanoffset+str.length()
      • the character at indexk-str.length() in the old character sequence, ifk is not less thanoffset+str.length()

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength 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 StringBuffer insert(int offset, char[] str)
      Inserts the string representation of thechar array argument into this sequence.

      The characters of the array argument are inserted into the contents of this sequence at the position indicated byoffset. 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 methodString.valueOf(char[]), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength 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 StringBuffer insert(int dstOffset,CharSequence s)
      Inserts the specifiedCharSequence into this sequence.

      The characters of theCharSequence 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'sinsert(dstOffset, s, 0, s.length()) method.

      The contents are unspecified if theCharSequence is modified during the method call or an exception is thrown when accessing theCharSequence.

      Ifs isnull, 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.
      Since:
      1.5

    • insert

      public StringBuffer insert(int dstOffset,CharSequence s, int start, int end)
      Inserts a subsequence of the specifiedCharSequence into this sequence.

      The subsequence of the arguments specified bystart andend 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 byend - start.

      The character at indexk in this sequence becomes equal to:

      • the character at indexk in this sequence, ifk is less thandstOffset
      • the character at indexk+start-dstOffset in the arguments, ifk is greater than or equal todstOffset but is less thandstOffset+end-start
      • the character at indexk-(end-start) in this sequence, ifk is greater than or equal todstOffset+end-start

      ThedstOffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      The start argument must be nonnegative, and not greater thanend.

      The end argument must be greater than or equal tostart, and less than or equal to the length of s.

      Ifs isnull, then this method inserts characters as if the s parameter was a sequence containing the four characters"null".

      The contents are unspecified if theCharSequence is modified during the method call or an exception is thrown when accessing theCharSequence.

      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()
      Since:
      1.5

    • insert

      public StringBuffer insert(int offset, boolean b)
      Inserts the string representation of theboolean argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(boolean), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      b - aboolean.
      Returns:
      a reference to this object.
      Throws:
      StringIndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset, char c)
      Inserts the string representation of thechar argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(char), and the character in that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      c - achar.
      Returns:
      a reference to this object.
      Throws:
      IndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset, int i)
      Inserts the string representation of the secondint argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(int), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      i - anint.
      Returns:
      a reference to this object.
      Throws:
      StringIndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset, long l)
      Inserts the string representation of thelong argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(long), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      l - along.
      Returns:
      a reference to this object.
      Throws:
      StringIndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset, float f)
      Inserts the string representation of thefloat argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(float), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength of this sequence.

      Parameters:
      offset - the offset.
      f - afloat.
      Returns:
      a reference to this object.
      Throws:
      StringIndexOutOfBoundsException - if the offset is invalid.

    • insert

      public StringBuffer insert(int offset, double d)
      Inserts the string representation of thedouble argument into this sequence.

      The overall effect is exactly as if the second argument were converted to a string by the methodString.valueOf(double), and the characters of that string were theninserted into this character sequence at the indicated offset.

      Theoffset argument must be greater than or equal to0, and less than or equal to thelength 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 valuek for which:

       this.toString().startsWith(str, k)
      If no such value ofk 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.
      Since:
      1.4

    • 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 valuek for which:

           k >= Math.min(fromIndex, this.length()) &&                   this.toString().startsWith(str, k)
      If no such value ofk 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.
      Since:
      1.4

    • 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 valuethis.length().

      The returned index is the largest valuek for which:

       this.toString().startsWith(str, k)
      If no such value ofk 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.
      Since:
      1.4

    • 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 valuek for which:

           k <= Math.min(fromIndex, this.length()) &&                   this.toString().startsWith(str, k)
      If no such value ofk 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.
      Since:
      1.4

    • reverse

      public StringBuffer 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. Letn be the character length of this character sequence (not the length inchar values) just prior to execution of thereverse method. Then the character at indexk in the new character sequence is equal to the character at indexn-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.
      Since:
      1.0.2

    • repeat

      public StringBuffer repeat(int codePoint, int count)
      Repeatscount copies of the string representation of thecodePoint argument to this sequence.

      The length of this sequence increases bycount times the string representation length.

      It is usual to usechar expressions for code points. For example:

      // insert 10 asterisks into the buffersb.repeat('*', 10);

      Parameters:
      codePoint - code point to append
      count - number of times to copy
      Returns:
      a reference to this object.
      Throws:
      IllegalArgumentException - if the specifiedcodePoint is not a valid Unicode code point or ifcount is negative.
      Since:
      21

    • repeat

      public StringBuffer repeat(CharSequence cs, int count)
      Appendscount copies of the specifiedCharSequencecs to this sequence.

      The length of this sequence increases bycount times theCharSequence length.

      Ifcs isnull, then the four characters"null" are repeated into this sequence.

      The contents are unspecified if theCharSequence is modified during the method call or an exception is thrown when accessing theCharSequence.

      Parameters:
      cs - aCharSequence
      count - number of times to copy
      Returns:
      a reference to this object.
      Throws:
      IllegalArgumentException - ifcount is negative
      Since:
      21

    • toString

      public String toString()
      Returns a string representing the data in this sequence. A newString object is allocated and initialized to contain the character sequence currently represented by this object. ThisString is then returned. Subsequent changes to this sequence do not affect the contents of theString.
      Specified by:
      toString in interface CharSequence
      Returns:
      a string representation of this sequence of characters.

    • chars

      public IntStream chars()
      Returns a stream ofint zero-extending thechar values from this sequence. Any char which maps to asurrogate 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 islate-binding). If the sequence is modified during that operation then the result is undefined.

      Specified by:
      chars in interface CharSequence
      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 byCharacter.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 toint 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 islate-binding). If the sequence is modified during that operation then the result is undefined.

      Specified by:
      codePoints in interface CharSequence
      Returns:
      an IntStream of Unicode code points from this sequence
      Since:
      9