Question

Given the following code:

Line 1 public class ClassA
Line 2 {
Line 3 public ClassA() {}
Line 4 public void method1(int a){}
Line 5 }

Line 6 public class ClassB extends ClassA
Line 7 {
Line 8 public ClassB(){}
Line 9 public void method1(){}
Line 10 }

Line 11 public class ClassC extends ClassB
Line 12 {
Line 13 public ClassC(){}
Line 14 public void method1(){}
Line 15 }

Which method1 will be executed when the following statements are executed?
ClassA item1 = new ClassB();
item1.method1();
Group of answer choices
a. none of these
b. method1 on line9
c. method1 on line14
d. method1 on line 4

Answer 1

The method1 on line 4 from ClassA will be executed since the method1 in ClassB does not override it, owing to a difference in method signature.

Therefore, the correct answer is: option d) method1 on line 4.

Step-by-step explanation:

Polymorphism in Java is the task that performs a single action in different ways. So, languages that do not support polymorphism are not 'Object-Oriented Languages', but 'Object-Based Languages'.

In this case, the method1 will be executed when the following statements are executed:

• ClassA item1 = new ClassB();
  item1.method1();

In this scenario, although ClassA is the type of the reference item1, an instance of ClassB is created and assigned to it.

However, the method1 in ClassB does not override the method1 in ClassA because it does not match the method signature (it lacks the parameter int a).

Therefore, when item1.method1(); is called, it will invoke the method1 on line 4 from ClassA, which is the only method that matches the method signature.