Section Name: Leader:
Edward Leon Knapp
Pre-Lab 09 CSC 127A Spring 2008 (15 points) Required Reading: Sections 7.1 7.7, 7.9, 7.10 Please read at least these sections of your text. Then answer the following questions and be prepared to turn them in at the beginning of your lab section on either 4/01 or 4/02. A word-processed write-up is preferred, but handwritten is acceptable as long as it is legible. You may NOT work with anyone else on this pre-lab. Topics: Defining a class, instance variables, writing class methods, writing constructors, access modifiers: public versus private, accessor and mutator methods, data manipulation methods, "this", toString and equals methods.
1. What is a Class definition composed of? A class definition normally is comprised with data that explains a person, place, or thing. The data of these classes are called fields. 2. What is the purpose of access modifiers? The purpose of an access modifier is to specify where the class or member of a class can be used. 3. What are instance variables? What code has access to them? The instance variables of a class hold the data for each object of that class. The code used to access instance variables is: accessModifier dataType indentifierList; 4. What is the general form of a method header (identify the parts that go into any method header and their purpose)? accessModifier returnType methodName ( parameter list )
5. What is a constructor and how does it differ from a regular method? A constructor is a special method that is called when an object is instantiated using a new keyword. This is different from the regular method because it uses a different keyword and a different syntax. 6. Does a class definition have to include a constructor? Why or why not? It is not necessary for the class definition to have a constructor because the compiler will provide a default constructor when the program is compiled.
Name: Section Leader:
Edward Leon Knapp
7. A class can have more than one constructor why is this desirable? would How they differ? It is desirable to have more than one constructor because it allows the program to take in more information and provide more results. It is more useful to have more than one constructor because more can be completed with the program. 8. What is the difference between accessor and mutator methods? The difference between the two methods is that accessor methods return the instance variable and is very simple while the mutator method changes the instance variable. A noticeable difference in the programming is that the accessor method begins with an uppercase letter whereas the mutator starts with a lowercase letter. 9. Can code written inside a method access other methods in the same class? Why or why not? If the code is written inside a method, it can access other methods as long as it is in the same class. This is because they are made of the same fields so the data inside the classes should be the same.
10. How does code outside a class definition use the code in a class? The code outside a class definition can only use the code in a class if the method to do so is defined earlier in the program. The data type and fields would also have to be defined for the codes. 11. When do you need to use this? This is used when a variable is not specifically defined throughout the program. It is used in order to specify the object throughout the program. 12. Can you write code so you never need to use this? Explain why/why not. Yes, you can write a program so that you never have to `this.' In order to write a program like that every object would need to be defined every time throughout the program. 13. You can use the toString method on an object of a class without defining it - what does it return and is it useful? Yes you can use the toString method on an object of a class without defining it. Typically it will return a string representing the object's fields and takes no parameters. It is mainly only useful while using the System.out.println
Name: Section Leader:
Edward Leon Knapp