Question

Java 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 method will be executed when the following statements are executed?
ClassC item1 = new ClassA();
item1.method1();
Group of answer choices
a.Line 4
b.LIne 14
c.Line 9

Answer 1

Due to a compilation error in the statement, none of the methods will execute. However, if the code is meant to instantiate ClassC, then the method in Line 14 would be executed. If a failed cast to ClassC is involved, a runtime exception will occur.

Step-by-step explanation:

The question revolves around Java inheritance and method overriding. Given the code and inheritance structure, ClassC extends ClassB, and ClassB extends ClassA. Method overriding allows a subclass to provide a specific implementation of a method that is already provided by one of its superclasses.

The Java code snippet provides three classes ClassA, ClassB, and ClassC, where ClassC is a subclass of ClassB, and ClassB is a subclass of ClassA. Each class defines a method1, but with different signatures. ClassA defines method1 with an integer parameter, and ClassB and ClassC define a parameterless method1, which is an example of overriding.

However, the code statement ClassC item1 = new ClassA(); is incorrect and would result in a compilation error, since ClassA cannot be assigned to a variable of type ClassC (Downcasting without an explicit cast is not allowed and even with a cast, it would cause a runtime exception if ClassA is not an instance of ClassC).

If the line was intended to be ClassC item1 = new ClassC();, then invoking item1.method1(); would execute the method defined in Line 14 of ClassC. If an explicit cast was used like ClassC item1 = (ClassC)new ClassA();, a runtime exception would occur at this line, since ClassA cannot be cast to ClassC.