CSC212 Lab 4 2014

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

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Lab 4 deals with private member variables, javadoc, and command line parameters. There are 2 Moodle submissions.

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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

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Javadoc

Adding the Javadoc Comments

• 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 the command line arguments.
         */
        public static void main(String[] args) {
                Animal a = new Animal( "Max", 3, false, true );
                a.displayBasicInfo();
                System.out.println();
        }

}

Create the Javadoc

• At the Linux prompt, 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	changes 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.

View the Javadoc

• Open a Web Browser, either on the Linux machine you are connected to, or on your laptop.
• In the URL bar, enter this URL, replacing the xx letters by your own 2-letter Id:

http://cs.smith.edu/~212a-xx/myjavadoc

• Verify that you get html pages describing your program. Explore the various pages and views of your program documentation.

Congratulations, you now know how to generate a sophisticated documentation package for your java programs!

Exercise

• Generate the javadoc for the Dog class, also available here.
• When generating the javadoc, use the following command:

javadoc -d ~/public_html/myjavadoc  Animal.java Dog.java

• Verify that you get both the dog and the animal classes listed on the front page of the html javadoc

Moodle Question

• Answer the Moodle question for Lab 4, Question 1. You have until Friday 11:55 p.m. to answer it.

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Accessing Command Line Arguments

• Create this new Java program:

class PrintArgs {

    public static void main( String[] args ) {

        for ( int i=0; i<args.length; i++ )
            System.out.println( 
                String.format( "args[%d] = %s", i, args[i] ) );

    }
}

• Run it and pass it several words on the command line, as illustrated below (try different combinations of words and numbers):

 javac PrintArgs.java
 java PrintArgs  1 2 3 4 5

 java PrintArgs Thursday afternoon lab on a warm September day

 java PrintArgs  "Smith College" is where "Sophia Smith" still lives

 java PrintArgs "Thursday afternoon lab on a warm September day"

 java PrintArgs "Thursday afternoon" lab on a warm September day

 java PrintArgs Thursday afternoon lab on a \"warm September\" day

Modification

• Modify the program so that if the first argument is "-up", the program will print all the arguments that follow in uppercase, otherwise it will display the arguments as it received them.
• To get the uppercase version of a string, use the toUpperCase() method of a String variable:

   String name = "Smith College";

   System.out.println(  name.toUpperCase() ); // will print SMITH COLLEGE

Example

[23:09:21] ~/public_html/classes/212$: java PrintArgs the quick red fox jumped over the dog
the 
quick
red
fox
jumped 
over
the
dog

[23:10:04] ~/public_html/classes/212$: java PrintArgs -up the "quick red fox" jumped over the dog
THE
QUICK RED FOX
JUMPED
OVER
THE
DOG
 

[23:11:38] ~/public_html/classes/212$: java PrintArgs

Note the lack of output for the last command!

Submission to Moodle

• Go to Moodle and select the "Lab 4, PrintArgs Virtual programming lab" test.
• Submit your PrintArgs.java program. You have until Friday 11:55 p.m. to submit it.

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Python List

• Recreate the "Python List" class we saw in class. Its code is available here.
• Add an index( n ) and rindex( n ) methods to the class.

• index( n ) will return the index, or location, of the first occurrence starting from Index 0, of n in the array, or -1 if n is not found.
• rindex( n ) will return the index, or location, of the first occurrence starting from the end of the array, of n in the array, or -1 if n is not found.
  
• Test your program thoroughly, and make sure both methods work correctly when:

• n is not in the array,
• there are multiple occurrences of n in the array,
• when the array contains only occurrences of n (for example, the array could be filled with 9 0s, and you are searching for index(0) and rindex(0),

* when n occurs only once in the array, at Index 0

* when n occurs only once in the array, in the last position of the array.