StringBuffer class

 

            Some methods below:  .insert(...),   .append(...),   .getChars(...),   setLength(...)

 

            For charAt(...)  and indexOf(...),   see String’s methods  charAt(...)  and  indexOf(...)

 

 

  A StringBuffer’s default capacity is 16 characters, if not specified otherwise in a constructor.  However StringBuffer capacities are automatically increased whenever necessary.  If they should overflow they just get automatically made longer.

 

  The concatenation  +  symbol is the same as the append(...) method for StringBuffer.  i.e 

 

sb = "a" + "b" + "c";           produces the same  abc  result as the same as the line below

StringBuffer sb =  new  StringBuffer( ).append("a").append("b").append("c");

 

  StringBuffer does not have an equals( ) method override like String and the wrapper classes do.

So for StringBuffer, == produces the same result as equals( ).  Both just look at the object pointer, not at the actual contents.

 

  StringBuffer does not have a shorthand form of its constructor, like String does.   i.e.

 

String s = "ABC";             works but

StringBuffer sb = "ABC";   won't compile.

You must say StringBuffer sb = new StringBuffer("ABC");

 

 

StringBuffer  .insert( offset, type )  method

 

    Works for many types, including boolean.  It inserts the automatic .valueOf  String representation of the second parm into the StringBuffer at the specified offset.  The offset starts at zero.

 

    It updates the original object’s  pointer.

 

 

 

StringBuffer  .append( type )  method

 

    Works for many types, including boolean.  Adds their String representation onto the end of this StringBuffer. It’s like doing an insert(...) at the end.

 

    Updates the object pointer.

 

 

void .getChars( srcBegin, srcEnd, char[  ] , dstBegin )  method

 

    Just like String's similar method.  It copies specified chars, from index srcBegin to index SrcEnd-1, copying them into a pre-existing char array starting at index dstBegin. 

 

   Will throw an IndexOutOfBoundsException if there’s anything wrong with any of the indexes. 

 

   This snippet copies the  a  and  b  from the StringBuffer onto the locations of the  4  and  5  in the original char array, printing the result  1 2 3 a b 6.

 

StringBuffer sb =  new  StringBuffer( ).append("a").append("b").append("c");

char[ ] ca = {'1', '2', '3', '4', '5', '6'};

sb.getChars( 0, 2, ca, 3 );

System.out.println(ca);

 

 

void .setLength( newlength )  method

 

    Resets a StringBuffer's length by either truncating it (if shorter) or padding it with \u0000's (if longer).