Introduction to Objects - Advanced Topics in Java: Core Concepts in Data Structures - page 45

The following will be printed:
Name of part: Air Filter
Price: $8.75
2.7 How to Name Your Java Files
If our program consists of a single public class, Java requires us to store such a class in a file called name of class .
java . So if the class is Palindrome , we must call the file Palindrome.java .
In the Part example, we must store the Part class in a file called Part.java , and we must store the PartTest class
in a file called PartTest.java . We could compile these classes with the following commands:
javac Part.java
javac PartTest.java
We could then run the test with this command:
java PartTest
Recall that this will execute main from the class PartTest . Note that it makes no sense to attempt something like
this:
java Part
If we do, Java will simply complain that there is no main method in the class Part .
We could, if we want, put both classes in one file. However, only one of the classes can be designated as public .
So, for example, we could leave class PartTest as it is and simply remove the word public from public class Part .
We could now put both classes in one file, which must be named PartTest.java since PartTest is the public class.
When we compile PartTest.java , Java will produce two files— PartTest.class and Part.class . We can then
run the test with this:
java PartTest
2.8 Working with Objects
So far, we have seen how to define a class and create objects from the class using a constructor. We have also seen how
to retrieve data from an object using accessor methods and how to change data in an object using mutator methods.
We now look at some issues that arise in working with objects.
2.8.1 Assigning an Object Variable to Another
An object variable ( p , say) is declared using a class name ( Part , say), like this:
Part p;
We emphasize again that p cannot hold an object but rather a pointer (or reference) to an object. The value of
p is a memory address—the location at which a Part object is stored. Consider the following:
Part a = new Part("Air Filter", 8.75);
Part b = new Part("Ball Joint", 29.95);