Package java.lang

Class StringBuffer

java.lang.Object
java.lang.StringBuffer
All Implemented Interfaces:
Serializable, Appendable, CharSequence
public final class StringBuffer
extends Object
implements Appendable, Serializable, CharSequence
A modifiable sequence of characters for use in creating strings, where all accesses are synchronized. This class has mostly been replaced by StringBuilder because this synchronization is rarely useful. This class is mainly used to interact with legacy APIs that expose it.

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 StringBuffer("a").append("b").append("c").toString().

Since:
1.0
See Also:
CharSequence, Appendable, StringBuilder, String, String.format(java.lang.String, java.lang.Object...), Serialized Form

  • Constructor Summary

    Constructors
    Constructor Description
    StringBuffer()
    Constructs a new StringBuffer using the default capacity which is 16.
    StringBuffer​(int capacity)
    Constructs a new StringBuffer using the specified capacity.
    StringBuffer​(CharSequence cs)
    Constructs a StringBuffer and initializes it with the content from the specified CharSequence.
    StringBuffer​(String string)
    Constructs a new StringBuffer containing the characters in the specified string.

  • Method Summary

    Modifier and Type Method Description
    StringBuffer append​(boolean b)
    Adds the string representation of the specified boolean to the end of this StringBuffer.
    StringBuffer append​(char ch)
    Adds the specified character to the end of this buffer.
    StringBuffer append​(char[] chars)
    Adds the character array to the end of this buffer.
    StringBuffer append​(char[] chars, int start, int length)
    Adds the specified sequence of characters to the end of this buffer.
    StringBuffer append​(double d)
    Adds the string representation of the specified double to the end of this StringBuffer.
    StringBuffer append​(float f)
    Adds the string representation of the specified float to the end of this StringBuffer.
    StringBuffer append​(int i)
    Adds the string representation of the specified integer to the end of this StringBuffer.
    StringBuffer append​(long l)
    Adds the string representation of the specified long to the end of this StringBuffer.
    StringBuffer append​(CharSequence s)
    Appends the specified CharSequence to this buffer.
    StringBuffer append​(CharSequence s, int start, int end)
    Appends the specified subsequence of the CharSequence to this buffer.
    StringBuffer append​(Object obj)
    Adds the string representation of the specified object to the end of this StringBuffer.
    StringBuffer append​(String string)
    Adds the specified string to the end of this buffer.
    StringBuffer append​(StringBuffer sb)
    Adds the specified StringBuffer to the end of this buffer.
    StringBuffer appendCodePoint​(int codePoint)
    Appends the string representation of the specified Unicode code point to the end of this buffer.
    int capacity()
    Returns the number of characters that can be held without growing.
    char charAt​(int index)
    Retrieves the character at the 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 beginIndex, int endIndex)
    Calculates the number of Unicode code points between start and end.
    StringBuffer delete​(int start, int end)
    Deletes a range of characters.
    StringBuffer deleteCharAt​(int location)
    Deletes the character at the specified offset.
    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[] buffer, int idx)
    Copies the requested sequence of characters to the char[] passed starting at idx.
    int indexOf​(String string)
    Searches for the first index of the specified character.
    int indexOf​(String subString, int start)
    Searches for the index of the specified character.
    StringBuffer insert​(int index, boolean b)
    Inserts the string representation of the specified boolean into this buffer at the specified offset.
    StringBuffer insert​(int index, char ch)
    Inserts the character into this buffer at the specified offset.
    StringBuffer insert​(int index, char[] chars)
    Inserts the character array into this buffer at the specified offset.
    StringBuffer insert​(int index, char[] chars, int start, int length)
    Inserts the specified subsequence of characters into this buffer at the specified index.
    StringBuffer insert​(int index, double d)
    Inserts the string representation of the specified into this buffer double at the specified offset.
    StringBuffer insert​(int index, float f)
    Inserts the string representation of the specified float into this buffer at the specified offset.
    StringBuffer insert​(int index, int i)
    Inserts the string representation of the specified integer into this buffer at the specified offset.
    StringBuffer insert​(int index, long l)
    Inserts the string representation of the specified long into this buffer at the specified offset.
    StringBuffer insert​(int index, CharSequence s)
    Inserts the specified CharSequence into this buffer at the specified index.
    StringBuffer insert​(int index, CharSequence s, int start, int end)
    Inserts the specified subsequence into this buffer at the specified index.
    StringBuffer insert​(int index, Object obj)
    Inserts the string representation of the specified object into this buffer at the specified offset.
    StringBuffer insert​(int index, String string)
    Inserts the string into this buffer at the specified offset.
    int lastIndexOf​(String string)
    Searches for the last index of the specified character.
    int lastIndexOf​(String subString, int start)
    Searches for the 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.
    StringBuffer replace​(int start, int end, String string)
    Replaces the characters in the specified range with the contents of the specified string.
    StringBuffer reverse()
    Reverses the order of characters in this buffer.
    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 current String representation.
    void trimToSize()
    Trims off any extra capacity beyond the current length.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    Methods inherited from interface java.lang.CharSequence

    length

  • Constructor Details

    • StringBuffer

      public StringBuffer()
      Constructs a new StringBuffer using the default capacity which is 16.

    • StringBuffer

      public StringBuffer​(int capacity)
      Constructs a new StringBuffer using the specified capacity.
      Parameters:
      capacity - the initial capacity.

    • StringBuffer

      public StringBuffer​(String string)
      Constructs a new StringBuffer containing the characters in the specified string. The capacity of the new buffer will be the length of the String plus the default capacity.
      Parameters:
      string - the string content with which to initialize the new instance.
      Throws:
      NullPointerException - if string is null.

    • StringBuffer

      public StringBuffer​(CharSequence cs)
      Constructs a StringBuffer and initializes it with the content from the specified CharSequence. The capacity of the new buffer will be the length of the CharSequence plus the default capacity.
      Parameters:
      cs - the content to initialize the instance.
      Throws:
      NullPointerException - if cs is null.
      Since:
      1.5

  • Method Details

    • append

      public StringBuffer append​(boolean b)
      Adds the string representation of the specified boolean to the end of this StringBuffer.

      If the argument is true the string "true" is appended, otherwise the string "false" is appended.

      Parameters:
      b - the boolean to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(boolean)

    • append

      public StringBuffer append​(char ch)
      Adds the specified character to the end of this buffer.
      Specified by:
      append in interface Appendable
      Parameters:
      ch - the character to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(char)

    • append

      public StringBuffer append​(double d)
      Adds the string representation of the specified double to the end of this StringBuffer.
      Parameters:
      d - the double to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(double)

    • append

      public StringBuffer append​(float f)
      Adds the string representation of the specified float to the end of this StringBuffer.
      Parameters:
      f - the float to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(float)

    • append

      public StringBuffer append​(int i)
      Adds the string representation of the specified integer to the end of this StringBuffer.
      Parameters:
      i - the integer to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(int)

    • append

      public StringBuffer append​(long l)
      Adds the string representation of the specified long to the end of this StringBuffer.
      Parameters:
      l - the long to append.
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(long)

    • append

      public StringBuffer append​(Object obj)
      Adds the string representation of the specified object to the end of this StringBuffer.

      If the specified object is null the string "null" is appended, otherwise the objects toString is used to get its string representation.

      Parameters:
      obj - the object to append (may be null).
      Returns:
      this StringBuffer.
      See Also:
      String.valueOf(Object)

    • append

      public StringBuffer append​(String string)
      Adds the specified string to the end of this buffer.

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

      Parameters:
      string - the string to append (may be null).
      Returns:
      this StringBuffer.

    • append

      public StringBuffer append​(StringBuffer sb)
      Adds the specified StringBuffer to the end of this buffer.

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

      Parameters:
      sb - the StringBuffer to append (may be null).
      Returns:
      this StringBuffer.
      Since:
      1.4

    • append

      public StringBuffer append​(char[] chars)
      Adds the character array to the end of this buffer.
      Parameters:
      chars - the character array to append.
      Returns:
      this StringBuffer.
      Throws:
      NullPointerException - if chars is null.

    • append

      public StringBuffer append​(char[] chars, int start, int length)
      Adds the specified sequence of characters to the end of this buffer.
      Parameters:
      chars - the character array to append.
      start - the starting offset.
      length - the number of characters.
      Returns:
      this StringBuffer.
      Throws:
      ArrayIndexOutOfBoundsException - if length < 0 , start < 0 or start + length > chars.length.
      NullPointerException - if chars is null.

    • append

      public StringBuffer append​(CharSequence s)
      Appends the specified CharSequence to this buffer.

      If the specified CharSequence is null the string "null" is appended, otherwise the contents of the specified CharSequence is appended.

      Specified by:
      append in interface Appendable
      Parameters:
      s - the CharSequence to append.
      Returns:
      this StringBuffer.
      Since:
      1.5

    • append

      public StringBuffer append​(CharSequence s, int start, int end)
      Appends the specified subsequence of the CharSequence to this buffer.

      If the specified CharSequence is null, then the string "null" is used to extract a subsequence.

      Specified by:
      append in interface Appendable
      Parameters:
      s - the CharSequence to append.
      start - the inclusive start index.
      end - the exclusive end index.
      Returns:
      this StringBuffer.
      Throws:
      IndexOutOfBoundsException - if start or end are negative, start is greater than end or end is greater than the length of s.
      Since:
      1.5

    • appendCodePoint

      public StringBuffer appendCodePoint​(int codePoint)
      Appends the string representation of the specified Unicode code point to the end of this buffer.

      The code point is converted to a char[] as defined by Character.toChars(int).

      Parameters:
      codePoint - the Unicode code point to encode and append.
      Returns:
      this StringBuffer.
      Since:
      1.5
      See Also:
      Character.toChars(int)

    • charAt

      public char charAt​(int index)
      Retrieves the character at the index.
      Specified by:
      charAt in interface CharSequence
      Parameters:
      index - the index of the character to retrieve.
      Returns:
      the char value.

    • codePointAt

      public int codePointAt​(int index)
      Retrieves the Unicode code point value at the index.
      Parameters:
      index - the index to the char code unit.
      Returns:
      the Unicode code point value.
      See Also:
      Character, Character.codePointAt(char[], int, int)

    • codePointBefore

      public int codePointBefore​(int index)
      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.
      See Also:
      Character, Character.codePointBefore(char[], int, int)

    • codePointCount

      public int codePointCount​(int beginIndex, int endIndex)
      Calculates the number of Unicode code points between start and end.
      Parameters:
      beginIndex - the inclusive beginning index of the subsequence.
      endIndex - the exclusive end index of the subsequence.
      Returns:
      the number of Unicode code points in the subsequence.
      See Also:
      Character, Character.codePointCount(char[], int, int)

    • delete

      public StringBuffer delete​(int start, int end)
      Deletes a range of characters.
      Parameters:
      start - the offset of the first character.
      end - the offset one past the last character.
      Returns:
      this StringBuffer.
      Throws:
      StringIndexOutOfBoundsException - if start < 0, start > end or end > length().

    • deleteCharAt

      public StringBuffer deleteCharAt​(int location)
      Deletes the character at the specified offset.
      Parameters:
      location - the offset of the character to delete.
      Returns:
      this StringBuffer.
      Throws:
      StringIndexOutOfBoundsException - if location < 0 or location >= length()

    • ensureCapacity

      public void ensureCapacity​(int min)
      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.

    • getChars

      public void getChars​(int start, int end, char[] buffer, int idx)
      Copies the requested sequence of characters to the char[] passed starting at idx.
      Parameters:
      start - the starting offset of characters to copy.
      end - the ending offset of characters to copy.
      buffer - the destination character array.
      idx - the starting offset in the character array.
      Throws:
      IndexOutOfBoundsException - if start < 0, end > length(), start > end, index < 0, end - start > buffer.length - index

    • indexOf

      public int indexOf​(String subString, int start)
      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:
      lastIndexOf(String,int)

    • insert

      public StringBuffer insert​(int index, char ch)
      Inserts the character into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      ch - the character to insert.
      Returns:
      this buffer.
      Throws:
      ArrayIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, boolean b)
      Inserts the string representation of the specified boolean into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      b - the boolean to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, int i)
      Inserts the string representation of the specified integer into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      i - the integer to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, long l)
      Inserts the string representation of the specified long into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      l - the long to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, double d)
      Inserts the string representation of the specified into this buffer double at the specified offset.
      Parameters:
      index - the index at which to insert.
      d - the double to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, float f)
      Inserts the string representation of the specified float into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      f - the float to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, Object obj)
      Inserts the string representation of the specified object into this buffer at the specified offset.

      If the specified object is null, the string "null" is inserted, otherwise the objects toString method is used to get its string representation.

      Parameters:
      index - the index at which to insert.
      obj - the object to insert (may be null).
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, String string)
      Inserts the string into this buffer at the specified offset.

      If the specified string is null, the string "null" is inserted, otherwise the contents of the string is inserted.

      Parameters:
      index - the index at which to insert.
      string - the string to insert (may be null).
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().

    • insert

      public StringBuffer insert​(int index, char[] chars)
      Inserts the character array into this buffer at the specified offset.
      Parameters:
      index - the index at which to insert.
      chars - the character array to insert.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if index < 0 or index > length().
      NullPointerException - if chars is null.

    • insert

      public StringBuffer insert​(int index, char[] chars, int start, int length)
      Inserts the specified subsequence of characters into this buffer at the specified index.
      Parameters:
      index - the index at which to insert.
      chars - the character array to insert.
      start - the starting offset.
      length - the number of characters.
      Returns:
      this buffer.
      Throws:
      NullPointerException - if chars is null.
      StringIndexOutOfBoundsException - if length < 0, start < 0, start + length > chars.length, index < 0 or index > length()

    • insert

      public StringBuffer insert​(int index, CharSequence s)
      Inserts the specified CharSequence into this buffer at the specified index.

      If the specified CharSequence is null, the string "null" is inserted, otherwise the contents of the CharSequence.

      Parameters:
      index - The index at which to insert.
      s - The char sequence to insert.
      Returns:
      this buffer.
      Throws:
      IndexOutOfBoundsException - if index < 0 or index > length().
      Since:
      1.5

    • insert

      public StringBuffer insert​(int index, CharSequence s, int start, int end)
      Inserts the specified subsequence into this buffer at the specified index.

      If the specified CharSequence is null, the string "null" is inserted, otherwise the contents of the CharSequence.

      Parameters:
      index - The index at which to insert.
      s - The char sequence to insert.
      start - The inclusive start index in the char sequence.
      end - The exclusive end index in the char sequence.
      Returns:
      this buffer.
      Throws:
      IndexOutOfBoundsException - if index is negative or greater than the current length, start or end are negative, start is greater than end or end is greater than the length of s.
      Since:
      1.5

    • lastIndexOf

      public int lastIndexOf​(String subString, int start)
      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.
      See Also:
      String.lastIndexOf(String,int)

    • offsetByCodePoints

      public int offsetByCodePoints​(int index, int codePointOffset)
      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.
      See Also:
      Character, Character.offsetByCodePoints(char[], int, int, int, int)

    • replace

      public StringBuffer replace​(int start, int end, String string)
      Replaces the characters in the specified range with the contents of the specified string.
      Parameters:
      start - the inclusive begin index.
      end - the exclusive end index.
      string - the string that will replace the contents in the range.
      Returns:
      this buffer.
      Throws:
      StringIndexOutOfBoundsException - if start or end are negative, start is greater than end or end is greater than the length of s.

    • reverse

      public StringBuffer reverse()
      Reverses the order of characters in this buffer.
      Returns:
      this buffer.

    • setCharAt

      public void setCharAt​(int index, char ch)
      Sets the character at the index.
      Parameters:
      index - the zero-based index of the character to replace.
      ch - the character to set.

    • setLength

      public void setLength​(int length)
      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 .
      Parameters:
      length - the new length of this StringBuffer.
      See Also:
      length()

    • subSequence

      public CharSequence subSequence​(int start, int end)
      Returns a CharSequence of the subsequence from the start index to the end index.
      Specified by:
      subSequence in interface CharSequence
      Parameters:
      start - the inclusive start index to begin the subsequence.
      end - the exclusive end index to end the subsequence.
      Returns:
      a CharSequence containing the subsequence.

    • substring

      public String substring​(int start)
      Returns the String value of the subsequence from the start index to the current end.
      Parameters:
      start - the inclusive start index to begin the subsequence.
      Returns:
      a String containing the subsequence.

    • substring

      public String substring​(int start, int end)
      Returns the String value of the subsequence from the start index to the end index.
      Parameters:
      start - the inclusive start index to begin the subsequence.
      end - the exclusive end index to end the subsequence.
      Returns:
      a String containing the subsequence.

    • toString

      public String toString()
      Returns the current String representation.
      Specified by:
      toString in interface CharSequence
      Returns:
      a String containing the characters in this instance.

    • trimToSize

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

    • capacity

      public int capacity()
      Returns the number of characters that can be held without growing.
      Returns:
      the capacity
      See Also:
      ensureCapacity(int), length()

    • length

      public int length()
      The current length.
      Returns:
      the number of characters contained in this instance.

    • indexOf

      public int indexOf​(String string)
      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.
      Since:
      1.4
      See Also:
      lastIndexOf(String)

    • lastIndexOf

      public int lastIndexOf​(String string)
      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.
      Since:
      1.4
      See Also:
      String.lastIndexOf(java.lang.String)