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Turn counter clockwise
Then Listing 7 calls the turn method causing the turtle to rotate its body by 135 degrees counter-clockwise. (A positive parameter causes a clockwise rotation and a negative parameter causes a counter clockwise rotation.)
Change the pen color and move forward again
Finally Listing 7 calls methods to change the pen color to blue and to cause the turtle to move forward by 150 pixels.
The final location
After making the turn, the turtle is facing southwest. Therefore, the forward movement causes a diagonal blue line to be drawn from theposition at the top of the yellow line down toward the southwest. As you can see in Figure 1 , the turtle comes to rest at the end of that line.
A few words about color
I have published extensively on the concept of color in Java. The best way to find that information is probably to go to Google and search for the keywords:
richard baldwin "color class" site:http://cnx.org/contents/
Google is also probably your best bet for finding information on other topics that I have published on various websites. For example, if you go to Google Images and search for the following keywords, you will find a lot of the work that I havepublished using Ericson's media library.
richard baldwin java ericson
Manipulate the turtle named sue
Listing 8 calls several methods on the object whose reference is stored in the variable named sue .
| Listing 8 . Manipulate the turtle named sue. |
|---|
sue.setName("sue");sue.setPenWidth(2);
sue.setPenColor(Color.RED);sue.moveTo(183,170);sue.setPenDown(false);sue.moveTo(216,203);
sue.setPenDown(true);sue.moveTo(250,237);}//end run method
}//end class Prob01Runner |
The end result
These method calls result in the turtle named sue facing north in the lower right corner of the window, having drawn the broken red line shown in Figure 1 in getting there.
The moveTo method
Listing 8 calls the moveTo method to cause the turtle to move to a new location on the basis of coordinate values instead of on the basis of a distance value.
Pen control
Listing 8 also calls the setPenDown method twice passing false and then true as the parameter to first raise and then lower the pen. This produced the gap in the red line shown in Figure 1 .
The Turtle class also provides methods named penUp and penDown that can be used to raise and lower the pen.
The end of the program
Listing 8 also signals the end of the method named run and the end of the class named Prob01Runner . As such, Listing 8 signals the end of the program.
II encourage you to copy the code from Listing 9 , compile it and execute it. Experiment with the code, making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.
II explained a program that uses Java and Ericson's media library to:
Stated in more detail, the program:
Notification Switch
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