public StrBuilder insert(final int index,String str){
  validateIndex(index);
  if (str == null) {
    str=nullText;
  }
  if (str != null) {
    final int strLen=str.length();
    if (strLen > 0) {
      final int newSize=size + strLen;
      ensureCapacity(newSize);
      System.arraycopy(buffer,index,buffer,index + strLen,size - index);
      size=newSize;
      str.getChars(0,strLen,buffer,index);
    }
  }
  return this;
}

public StrBuilder insert ( final int index , String str ) { validateIndex ( index ) ; if ( str == null ) { str = nullText ; } if ( str != null ) { final int strLen = str . length ( ) ; if ( strLen > 0 ) { final int newSize = size + strLen ; ensureCapacity ( newSize ) ; System . arraycopy ( buffer , index , buffer , index + strLen , size - index ) ; size = newSize ; str . getChars ( 0 , strLen , buffer , index ) ; } } return this ; }
inserts the string into this builder . inserting null will use the stored null text value .
