Methods: Communicating with Objects
We communicate with objects using methods. Methods are executable code within each object, for which an interface has been established. Sometimes the interface is only for the object itself. Other times it is an interface accessible by other objects. This chapter discusses that topic in detail.
3.2 Passing Information to an Object
Passing keyboard input to takeSticks()
To complete this section, let’s modify our main() method in Figure 3.2
so that it prompts the user to input an integer from the keyboard and
then uses a Scanner object, introduced in the previous chapter, to read
the integer. That integer will then be used as the argument in a call to
takeSticks(). These modifications have been incorporated into the
revised version of the main() method shown in Figure 3.4. If we now
run this program the following output will be generated in the console
window before waiting for keyboard input:
If the user then inputs a 2 from the keyboard, that input will be read
and the takeSticks() method will remove 2 sticks. The output in the
console window will now look like:
SELF-STUDY EXERCISES
EXERCISE 3.1 Explain the difference between a method declaration and a method invocation.
EXERCISE 3.2 Explain the difference between a formal parameter and an argument.
EXERCISE 3.3 Modify the OneRowNim class of Figure 3.4 by adding two instance variables of type String to store names of the two players. Choose names for the instance variables that would be appropriate for storing names for player one and player two. Write a method named setNames() with two string parameters which assigns the first parameter to the instance variable that you created for the name of player one. The second parameter should be assigned to the other new instance variable.
EXERCISE 3.4 Write a statement that calls the setName() method of
the previous exercise and sets the name of player one of game to “Xena”
and sets the name of player two to “Yogi”.