CSC212 Lab 4 2014

--D. Thiebaut (talk) 21:12, 17 September 2014 (EDT)

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Lab 4 deals with private member variables, and javadoc.

Private Member Variables

• Login to beowulf2.csc.smith.edu, grendel.csc.smith.edu, or use one of the Linux Mint machines.
• Create a new program called Animal1.java containing the code below:

public class Animal1 {
        boolean isVaccinated;
        boolean isTattooed;
        String name;
        int age;
        
        Animal1( String n, int a, boolean v, boolean t ) {
                name             = n;
                age              = a;
                isVaccinated = v;
                isTattooed   = t;
        }
        
        public void displayBasicInfo( ) {
                String v = "vaccinated";
                if ( !isVaccinated ) v = "not " + v;
                String t = "tattooed";
                if ( !isTattooed ) t = "not " + t;
                System.out.println( String.format( "%s (%d), %s, %s", 
                                name, age, t, v ) );
        }
        
}

• In the same directory, create a second file called TestAnimal1.java, which contains this code:

class TestAnimal1 {

   TestAnimal1() { 
   }

   public static void main(String[] args) {
           // create a new animal
           Animal1 a = new Animal1( "Max", 3, false, true );
           a.displayBasicInfo();

           // modify it.  Then display it.
           a.isVaccinated = true;
           a.isTattooed = false;
           a.age = 5;
           a.displayBasicInfo();

           // modify it some more, then display it.
           a.isTattooed = ! a.isTattooed;
           a.age = a.age + 1;
           a.displayBasicInfo();
   }
}

• Compile and run both:

 javac Animal1.java TestAnimal1.java
 java TestAnimal1

• Verify that you get the following output:

Max (3), tattooed, not vaccinated
Max (5), not tattooed, vaccinated
Max (6), tattooed, vaccinated

Modification

• Modify the Animal1.java program and make all its member variables private.

        private boolean isVaccinated;
        private boolean isTattooed;
        private String name;
        private int age;

• Recompile both java programs. Notice that, now, TestAnimal1.java generates many errors. Why?
• If you answer that it is because TestAnimal1 cannot access the member variables of a any longer, you are right!
• Modify both Animal1 and TestAnimal1 so that

• Animal1 will now have mutator and inspector methods to access its member functions, and
• TestAnimal1 will access the member variables of a by using the new accessors and mutators

• Here is an example of a modification you can make on Animal1.java

         // mutator
         public void setAge( int n ) {
               age = n;
         }

         // ispector
         public int getAge( ) {
               return age;
         }

• And here is an example of a modification you can make on TestAnimal1.java:

        a.setAge( 5 );

• When you have been able to get rid of all the compiler errors for TestAnimal1.java, run the program TestAnimal1 and verify that you get the same output as before:

Max (3), tattooed, not vaccinated
Max (5), not tattooed, vaccinated
Max (6), tattooed, vaccinated

Javadoc

• You need to be connected to your 212a-xx account on one of the Linux machines for this all section to work.
• Locate your old Animal.java class from a previous lab, or copy/paste it from here.
• Don't worry if the member variables are not private. In this section we're interested in generating the javadoc for this program.
• Add documentation to your program using the same format as shown below. While it might be tempting to copy/paste it, please type it. It's the best way to remember how the javadoc syntax works:

/**
 * implements a base class for an animal.
 * @author thiebaut
 *
 */
public class Animal {

        private boolean isVaccinated;	// boolean holding the property for vaccination
        private boolean isTattooed;		// boolean holding the property for tattoo
        private String name;			// contains the animal's name
        private int age;				// equal to the animal's age
        
        /**
         * constructor
         * @param n the name of the animal
         * @param a the age of the animal
         * @param v	true if animal is vaccinated, false otherwise
         * @param t true if animal is tattooed, false otherwise
         */
        Animal( String n, int a, boolean v, boolean t ) {
                name             = n;
                age              = a;
                isVaccinated = v;
                isTattooed   = t;
        }
        
        /**
         * displays all the information about the animal.
         * <P>
         * Format:<br />
         * Rex (3), tattoed, not vaccinated
         */
        public void displayBasicInfo( ) {
                String v = "vaccinated";
                if ( !isVaccinated ) v = "not " + v;
                String t = "tattooed";
                if ( !isTattooed ) t = "not " + t;
                System.out.print( String.format( "%s (%d), %s, %s", 
                                name, age, t, v ) );
        }
        
        /**
         * Main entry point.
         * @param args
         */
        public static void main(String[] args) {
                Animal a = new Animal( "Max", 3, false, true );
                a.displayBasicInfo();
                System.out.println();
        }

}

• Enter the following commands:

command	description
javadoc -d ~/public_html/myjavadoc Animal.java	creates the javadoc for Animal.java, and stores the resulting html files in the public_html folder of your home directory, in a subdirectory called myjavadoc. The -d switch specifies that we want the output files generated to go into a specific directory.
chmod -R a+rx ~/public_html/myjavadoc	change the access permissions to all the files belonging to the subirectory you just created, named myjavadoc, in the directory public_html in your account. -R means: visit recursively all the files and subdirectories found inside myjavadoc. a+rx means: allow all to read and execute the files found. This way the Web Server on beowulf2 will be able to make your files available when requested by a Web browser.