how to fix "Cannot find symbol"

[etri]

import TurtleGraphics. *;
public class Square
{
private Turtle yertle;
public Square()
{
yertle = new Turtle (TGCanvas(700,4 0));
//yertle.penDown( );
yertle.forward( 40);
//yertle.penUp();
}
public static void main ( String args [])
{
new Square();
}
}