Question

What output is produced by the following code? Explain how it works (at least 5 lines).

class Super {
int num = 1;
int id = 2;
}

class Sub extends Super {
int num = 3;

public void display() {
System.out.println(num);
System.out.println(super.num);
System.out.println(id);
}
}

public class Inheritance1 {
public static void main (String[] args) {
Sub obj = new Sub();
obj.display();
}
}

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Example of "Explain how it works"

Sample Question:
What output is produced by the following code?   Explain how it works.

class student {

    String name;

    int age;

}

public class q6_ArryList1 {

public static void main(String args[]) {

      ArrayList<student>myArray = new ArrayList<>();

       for(int i=0; i< 4; i++){

         student s = new student();      

         s.name="Emily"+i;

         myArray.add(s);  

      }

    for (int i = 0; i<myArray.size(); i++){

        System.out.format("%s %n", myArray.get(i).name, myArray.get(i).age);

     }

    System.out.println();

    for (int i = 0; i<myArray.size(); i++){

       if (i % 2 ==0) {

        myArray.remove(1); }

    }

   for (int i = 0; i<myArray.size(); i++){

     System.out.format("%s %n", myArray.get(i).name, myArray.get(i).age);

    }

}

}

Answer:

Emily 0
Emily 1
Emily 2
Emily 3
Emily 0
Emily 3

How it works:
In this problem, an arrayList is created, then Emily + i is added to the arrayList where i is the for loop variable. The for loop goes from 0 inclusive to 4 exclusive. Therefore the arrayList contains [Emily0,Emily1, Emily2, Emily3]. After this, another for loop that goes through the arrayList is executed. An if statement inside the for loop gives a condition that if i %2 = 0, then remove the value at position 1. Thus, at 0, index 1 which is Emily1 is removed. At 1, nothing is removed. At 2, Emily2 is removed. Lastly, the arrayList, which contains[Emily0 and Emily3] is printed.

Answer 1

Short Summary:

• Provided the output and explanation for the requirement

Answer:

3

1

2

Explanation:

• Super is the base or parent class which has instance variables num and id as initialized to 1 and 2 respectively. Sub is the child class which is inherited from Super class. Sub class initialized num to 3. Object is created for Sub class inside main function. Using the sub class object created calling the display method. When display is called, it prints out local num value as 3 and super.num value will be 1 that from parent class and id value of 2 which can be directly access from parent class

  

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