public StrBuilder ensureCapacity(final int capacity){
  if (capacity > buffer.length) {
    final char[] old=buffer;
    buffer=new char[capacity * 2];
    System.arraycopy(old,0,buffer,0,size);
  }
  return this;
}

public StrBuilder ensureCapacity ( final int capacity ) { if ( capacity > buffer . length ) { final char [ ] old = buffer ; buffer = new char [ capacity * 2 ] ; System . arraycopy ( old , 0 , buffer , 0 , size ) ; } return this ; }
checks the capacity and ensures that it is at least the size specified .
