CPE 102

Winter 2008

Lab 1

                 

Errata:

 

None – any updates or corrections will appear here.

 

Objectives

 

• To be able to develop and use a simple Java class.
• To be able to develop and run a complete Java program.
• To become familiar with the Integrated Development Environment (IDE) of your choice.
• To be able to compile and run a Java program in your IDE.
• To be able to compile and run a Java program on hornet from the command-line.
• To be able to turn in your source code electronically on hornet.
• To become familiar with JUnit tests.
• To be able to compile and run JUnit tests in your IDE.

 

Resources

 

1. Your text.
2. Your peers.
3. Your instructor.
4. The Java Standard Library – Book-mark this web page, you will be using the Java Standard Library documentation regularly this quarter. Find String in the alphabetic ordered “All Classes” frame and pay special attention to the discussion of the “+” operator for string concatenation – especially useful for this lab. 
5. Handin Reference
6. JCreator and JUnit Integration reference
7. JGrasp and JUnit Integration reference

 

Ground Rules

 

None

 

Orientation

 

You will be developing a Java program comprised of three files (one source file, one test file, and one test driver) that will be able to greet a person by name.  The source file will contain a simple Java class to support greeting a person by name.  This class will be a server-class, i.e., it provides services to another piece of code.  The test file will check the class's expected interface and validate its correctness. The test driver will execute the test file and report to the user about successes and failures.

 

Specification

 

1. You must implement the classes and methods exactly as described.

 

2. Be sure all instance variables are declared as private.

 

3. Include the following comment block at the beginning of every source file:

 

/**

 * Provide a brief description of what the source file is/does

 *

 * @author Your Name Here

 * @version Lab X (replace X with the actual lab number)

 * @version CPE102-X (replace the X with your section number)

 * @version Winter 2008

 */

 

4. Write a class called Greeter in a file named Greeter.java (in java class names and file names must match or your code will not compile).  At this point you should be able to successfully compile your code – do so before continuing.

 

5. Implement a constructor in the Greeter class that accepts a String representing the name of a person to greet.  Notice that constructors are special methods that have no return type and must have the name of the class.  There can be more than one constructor per class – they will all have the same name but must have different parameters (this is called overloading).  Use the String parameter to initialize a private instance variable (also of type String) that will be used later by another method of the class.  This instance variable represents the state of the object.  Compile your code and fix any errors before continuing.

 

6. Implement a method called greet that is public, has a return type of String, and has no parameters.  The method must return the following greeting:

     

            “Hello name”

 

where name is replaced with the name that was passed to the constructor and used to initialize the object’s instance variable.  See the Resources section above for help with concatenation of strings.  Compile your code and fix any errors before continuing.

 

7. To test your Greeter class's validity, we will use the JUnit testing framework. First, make sure that you have JUnit installed and integrated with JGrasp or JCreator, or your favorite IDE. Download and compile my test file and test driver. Make sure you understand what is going on in the testGreet() method in the GreeterTest class.
   
   Note that the test driver, AllTests.java, contains a main method. The method signature must appear as shown to result in a valid Java program.  This is the entry-point the Java Virtual Machine requires to run your program.  Notice the use of the word static - this means the method can be called without an object of the class that contains the method existing (more later in the quarter about that).  The parameter type is an array of String objects that represent the command-line arguments to the program, if any.

 

8. Execute the program defined in the AllTests class. You should see output reporting to you that one test ran and that it completed successfully. The output should look something like this:
   .
   Time: 0.015
   
   OK (1 test)
   
   
   The . represents one test that was run.
   
   Now, in the testGreet() method, change the value assigned to name to your own name, and modify the call to assertEquals to match. How do you expect this to affect the test results? Recompile GreeterTest.java and re-run the application. Did the output match your expectations?
   
   Now, in the testGreet() method, change the final line to:
   
                   assertEquals("Goodbye [insert name here]", greeting);
   
   where [insert name here] is replaced with name's value. How do you expect this to affect the test results? Recompile GreeterTest.java and re-run the application. Did the output match your expectations?
    

9. Now that you have tested your Greeter class and you are confident that it works correctly, let's use it in an interactive program. In a new file, write a class called Driver.  Do you know what name the file must have?  If not, read item 4 above more carefully before continuing.  This class should have the following method in it:

 

/**

 * Don’t forget the required comment block specified above!

 */

import java.util.Scanner;

 

public static void main(String[] args)

{

   // Declare and construct a Scanner object to read from the command-line

   Scanner scanner = new Scanner(System.in);

 

   // Prompt for a name

   System.out.print(“What is your name? “);

 

   // Read the name using the Scanner

   String name = scanner.nextLine();

 

   // Construct a Greeter object

   Greeter greeter = new Greeter(name);

 

   // Get the greeting and save it to a String

   String greeting = greeter.greet();

 

   // Display the greeting to the command-line

   System.out.println(greeting);

}

 

The method signature must appear as shown to result in a valid Java program.  This is the entry-point the Java Virtual Machine requires to run your program.  Notice the use of the word static – this means the method can be called without an object of the class that contains the method existing (more later in the quarter about that).  The parameter type is an array of String objects that represent the command-line arguments to the program, if any.

 

10. Here is what a sample run of your complete program should look like.  Notice that the arrows represent shell prompts and may or may not appear, depending on what IDE/environment you are running your program in.  Also note that the bold John Doe is user input not program output.

 

>       What is your name? John Doe

>       Hello John Doe

 

 

Suggestions

 

None