Build it step by step

Every step below leaves a scenario that compiles and runs. If you stop halfway you will have something that works, not something broken. Follow along in Greenfoot rather than reading straight through.

1. Step 1

   On your screen Greenfoot documentation for the Actor class showing the signature of the move method.

   void move(int distance)

   Read it left to right and it answers both questions.

   `void` is the return type: this method hands nothing back. `move` is the name. `(int distance)` is the parameter list: you must supply one whole number, and inside the method it will be called distance.

   So a legal call is move(4). Not move(). Not move("far"). One whole number.

2. Step 2

   On your screen Documentation showing the getX method signature with an empty parameter list and an int return type.

   int getX()

   This one is the mirror image. `int` means it hands back a whole number. `()` empty means it needs nothing from you.

   That difference changes how you use it. move(4) is a complete instruction on its own. getX() is a question, and a question you never listen to the answer of is pointless.

3. Step 3

   On your screen A crab in the world with its current x coordinate displayed in a Greenfoot result dialog.

   int where = getX();

   One way to listen: store the answer. `getX()` runs and produces a number; `int where =` catches it and gives it a name. Now you can use `where` as many times as you like.

4. Step 4

   On your screen The crab shifted one cell to the right after a setLocation call built from getX and getY.

   setLocation(getX() + 1, getY());

   The other way: use the answer immediately, inside another call. Read this from the inside out. getX() gives the current x. Add 1. getY() gives the current y, unchanged. Hand both to setLocation.

   The result is "move one cell right, whichever way I happen to be facing". You will write this exact line in Unit 2 to make arrow keys work, so it is worth reading twice.