Question

Provide code and assertion statements for the pre/post-conditions. (To execute the assertion code, the java.exe requires the option -ea for the VM).

// ***  MyArrayList is limited to 100 elements.  ***
public class MyArrayList<E> extends ArrayList<E> {

    public MyArrayList() {
        // assert postcondition
    }

    @Override
    public int size() {
        // assert postcondition
        // code
    }

    // Insert e as a new first element to mal
    public void insertFirst(E e) {
        // assert precondition
        // code
        // assert postcondition
    }

    // Insert e as a new last element
    public void insertLast(E e) {
        // assert precondition
        // code
        // assert postcondition
    }

    // Delete my first element
    public void deleteFirst() {
        // assert precondition
        // code
        // assert postcondition
    }

    // Delete my last element
    public void deleteLast() {
        // assert precondition
        // code
        // assert postcondition
    }

    public void show() {
        for (E e : this) {
            System.out.println(e);
        }
    }
}

public class Student {
     // code
}

public class MyProg {
    public static void main(String[] args) {
        MyArrayList<Student> mal = new MyArrayList<>();
        mal.insertFirst(new Student(1, "John"));
        mal.insertFirst(new Student(2, "Mary"));
        mal.insertLast(new Student(3, "Mike"));
        mal.show();
        mal.deleteLast();
        mal.show();       
        mal.deleteFirst();
        mal.show();

    }
  }

// ------------------- EXPECTED OUTPUT --------------------- //

The following is the execution output if all assertions are valid and passed:

2, Mary

1, John

3, Mike

2, Mary

1, John

1, John

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// MyArrayList.java

import java.util.ArrayList;

public class MyArrayList<E> extends ArrayList<E> {

      // maximum number of elements in MyArrayList

      private static final int MAX_SIZE = 100;

      public MyArrayList() {

            // assert postcondition

            assert size() == 0;

      }

      @Override

      public int size() {

            // assert postcondition, that size is always less than or equal to

            // MAX_SIZE

            assert super.size() <= MAX_SIZE;

            // code, invoking size method of super class and returning it

            return super.size();

      }

      // Insert e as a new first element

      public void insertFirst(E e) {

            // assert precondition, that MyArrayList is not full

            assert size() < MAX_SIZE;

            // code

            super.add(0, e);

            // assert postcondition, that first element is e

            assert get(0).equals(e);

      }

      // Insert e as a new last element

      public void insertLast(E e) {

            // assert precondition, that MyArrayList is not full

            assert size() < MAX_SIZE;

            // code

            super.add(e);

            // assert postcondition, that last element is e

            assert get(size() - 1).equals(e);

      }

      // Delete my first element

      public void deleteFirst() {

            // assert precondition, that list is not empty

            assert size() > 0;

            // recording current size

            int currSize = size();

            // code

            super.remove(0);

            // assert postcondition, that size is now reduced by 1

            assert size() == currSize - 1;

      }

      // Delete my last element

      public void deleteLast() {

            // assert precondition that list is not empty

            assert size() > 0;

            int currSize = size();

            // code

            super.remove(currSize - 1);

            // assert postcondition, that size is now reduced by 1

            assert size() == currSize - 1;

      }

      public void show() {

            for (E e : this) {

                  System.out.println(e);

            }

      }

}

// Student.java

public class Student {

      // id and name of student

      private int id;

      private String name;

      // constructor initializing id and name

      public Student(int id, String name) {

            this.id = id;

            this.name = name;

      }

      @Override

      public String toString() {

            // returning id and name separated by comma and space

            return id + ", " + name;

      }

}

//No change is made to MyProg.java

/*OUTPUT*/

2, Mary

1, John

3, Mike

2, Mary

1, John

1, John