Question

Given the following definition of class Aclass:

           

class Aclass

{

private char letter;

                        private int value;

public Aclass( )

{

Letter =  ‘A’;        

value = 0;

                        }

                        public Aclass( char ch, int num)

{

letter = ch;

value = num;

                        }

                        public int getvalue( )

{

return value;

}

public void print( )

{

System.out.println( “letter =” + letter + “\n value =” + value);

                        }

            }

A.   ( 20 pts )

1. Write the definition of the class named Bclass as follows:

• It has the private instance variable firstm (integer) and secondm (reference variable of the class Aclass).
• It has the default constructor (the initial value for instance variable firstm is 10) and the constructor with a parameter for each of its instance variables.
• It has a public instance method void print( ) that outputs the values of its instance variables.
• It has a public instance method int computeSum(   ) that computes and returns the sum of the instance variables secondm.value and firstm.

2. Write a statement to define the object of the class Bclass named bobj initialized with the value ‘Z’ for instance variable secondm.letter, 20 for instance variable secondm.value, and 30 for instance variable firstm.

B.  ( 27 pts )

1. Write the definition of the class named Cclass that extends class Aclass as follows:

• It has an additional private instance variable firstm (integer value).
• It has the default constructor (the initial value for instance variable firstm is 10) and the constructor with a parameter for each of its instance variables.
• The instance method print( ) is overridden in this class: it also outputs the value of instance variable firstm in addition to the instance variables inherited.
• It has a public instance method int computeSum(   ) that computes and returns the sum of the instance variables value and firstm.

Assume given the following definitions of objects and static method process( ):

      Aclass   aobj1 = new Aclass( ‘B’, 5) ;

Aclass aobj2 = new Cclass( ‘Z’, 20, 30 ),;

      Cclass cobj = new Cclass( ‘K’, 90, 70 );

      static void process( Aclass obj )

      {

                  obj.print(   );

      }

1. Show the output produced by each of the following statements:

                        aobj1.print(   );

                        aobj2.print(   );

                        process( aobj1 );

                        process( cobj );

1. Is the statement             aobj2.computeSum(   ); legal? Explain. If it is not legal, how would you correct the problem?

                       

A.     Define and instantiate the array Alist of 10 objects of the class Aclass. Each object in the array is initialized with the default constructor.  (6 pts)

Answer 1

Below are your classeS:

Bclass.java

class Bclass {
        private int firstm;
        private Aclass secondm;

        Bclass() {
                this.firstm = 10;
                secondm = new Aclass();
        }

        public Bclass(int firstm, Aclass secondm) {
                this.firstm = firstm;
                this.secondm = secondm;
        }

        public void print() {
                System.out.println("firstm=" + firstm);
                System.out.println("secondm: ");
                secondm.print();
        }

        public int computeSum() {
                return this.firstm + secondm.getvalue();
        }

        public static void main(String[] args) {
                Bclass bobj = new Bclass(30, new Aclass('Z', 20));
                System.out.println("Value of bobj: ");
                bobj.print();
                System.out.println("Sum: " + bobj.computeSum());
        }

}

Output

Cclass.java

public class Cclass extends Aclass {
        private int firstm;

        public Cclass() {
                super();
                this.firstm = 10;
        }

        public Cclass(char ch, int num, int firstm) {
                super(ch, num);
                this.firstm = firstm;
        }

        @Override
        public void print() {
                System.out.println("firstm: " + this.firstm);
                super.print();
        }

        public int computeSum() {
                return this.firstm + super.getvalue();
        }

}

First question:

Assume given the following definitions of objects and static method process( ):

      Aclass   aobj1 = new Aclass( ‘B’, 5) ;

Aclass aobj2 = new Cclass( ‘Z’, 20, 30 ),;

      Cclass cobj = new Cclass( ‘K’, 90, 70 );

      static void process( Aclass obj )

      {

                  obj.print(   );

      }

1. Show the output produced by each of the following statements:

                        aobj1.print(   );

                        aobj2.print(   );

                        process( aobj1 );

                        process( cobj );

For this changed Cclass as follows:

public class Cclass extends Aclass {
        private int firstm;

        public Cclass() {
                super();
                this.firstm = 10;
        }

        public Cclass(char ch, int num, int firstm) {
                super(ch, num);
                this.firstm = firstm;
        }

        @Override
        public void print() {
                System.out.println("firstm: " + this.firstm);
                super.print();
        }

        public int computeSum() {
                return this.firstm + super.getvalue();
        }

        public static void main(String[] args) {
                Aclass aobj1 = new Aclass('B', 5);

                Aclass aobj2 = new Cclass('Z', 20, 30);

                Cclass cobj = new Cclass('K', 90, 70);
                
                  aobj1.print(   );

          aobj2.print(   );

          process( aobj1 );

          process( cobj );
        }

        static void process(Aclass obj)

        {

                obj.print();

        }
}

Output

letter =B
value =5
firstm: 30
letter =Z
value =20
letter =B
value =5
firstm: 70
letter =K
value =90

Second Question:

is aobj2.computeSum(   ); legal

No because aobj2 is object of Aclass and Aclass doesnt have computeSum function

Third Question

If it is not legal, how would you correct the problem?

To correct it we need to change below line

Aclass aobj2 = new Cclass('Z', 20, 30);

to

Cclass aobj2 = new Cclass('Z', 20, 30);

This will solve the issue

Fourth Question:

Define and instantiate the array Alist of 10 objects of the class Aclass. Each object in the array is initialized with the default constructor.

Aclass Alist[] = new Aclass[10];
Alist[0] = new Aclass();
Alist[1] = new Aclass();
Alist[2] = new Aclass();
Alist[3] = new Aclass();
Alist[4] = new Aclass();
Alist[5] = new Aclass();
Alist[6] = new Aclass();
Alist[7] = new Aclass();
Alist[8] = new Aclass();
Alist[9] = new Aclass();