docs: public static Matrix createMatrix(int rowCount, int colCount) {
  		if (rowCount<=0 || colCount<=0) throw new IllegalArgumentException();
  		if (colCount==1)
  			return createVector(rowCount);
  		else if (rowCount==2 && colCount==2)
  			return createMatrix2();
  		else if (rowCount==3 && colCount==3)
  			return createMatrix3();
  		else
  			return new MatrixImpl(rowCount, colCount);
  	}