What is the output of running class C? class A { public A() { System.out.println( "The default constructor of A is invoked"); } } class B extends A { public B() { System.out.println( "The default constructor of B is invoked"); } } public class C { public static void main(String[] args) { B b = new B(); } } Group of answer choicesNothing displayed"The default constructor of B is invoked""The default constructor of A is invoked" followed by "The default constructor of B is invoked""The default constructor of B is invoked" followed by "The default constructor of A is invoked""The default constructor of A is invoked"
Question
What is the output of running class C? class A { public A() { System.out.println( "The default constructor of A is invoked"); } } class B extends A { public B() { System.out.println( "The default constructor of B is invoked"); } } public class C { public static void main(String[] args) { B b = new B(); } } Group of answer choicesNothing displayed"The default constructor of B is invoked""The default constructor of A is invoked" followed by "The default constructor of B is invoked""The default constructor of B is invoked" followed by "The default constructor of A is invoked""The default constructor of A is invoked"
Solution 1
The output of running class C will be "The default constructor of A is invoked" followed by "The default constructor of B is invoked".
Here's why:
When you create an object of class B using new B(), the Java Virtual Machine (JVM) first calls the constructor of class B. However, because B is a subclass of A, before executing the B constructor, it calls the constructor of class A (the superclass).
So, the constructor of class A is invoked first, printing "The default constructor of A is invoked". After that, the constructor of class B is invoked, printing "The default constructor of B is invoked".
Therefore, the output will be:
The default constructor of A is invoked
The default constructor of B is invoked
Solution 2
The output of running class C will be "The default constructor of A is invoked" followed by "The default constructor of B is invoked".
Here's why:
-
When you create an instance of class B with "new B()", the Java Virtual Machine (JVM) first calls the constructor of class B.
-
However, because B is a subclass of A, before executing the B constructor, it first calls the constructor of the superclass A. This is why "The default constructor of A is invoked" is printed first.
-
After the A constructor has finished, the JVM then executes the rest of the B constructor, printing "The default constructor of B is invoked".
So, the constructors are called in the order from the top of the inheritance tree (superclasses) down (subclasses).
Similar Questions
What is the output of running class C? _____ A. "The default constructor of B is invoked"B. "The default constructor of A is invoked" followded by "The default constructor of B is invoked"C. "The default constructor of B is invoked" followed by "The default constructor of A is invoked"D. "The default constructor of A is invoked"
Analyze the following code carefully. Please select all that apply. public class Test { public static void main(String[] args) { A a = new A(); a.print(); } } class A { String s; A(String s) { this.s = s; } void print() { System.out.println(s); } } Group of answer choicesThe program has a compile error because class A is not a public class.The program has a compile error because class A does not have a default constructor.The program compiles and runs fine and prints nothing.The program would compile and run if you change A a = new A() to A a = new A("5").
Analyze the following code and choose two correct statements from below. public class Test extends A { public static void main(String[] args) { Test t = new Test(); t.print(); } } class A { String s; A(String s) { this.s = s; } public void print() { System.out.println(s); } } Group of answer choicesThe program does not compile because Test does not have a default constructor Test().The program has an implicit default constructor Test(), but it cannot be compiled, because its super class does not have a default constructor. The program would compile if the constructor in the class A were removed.The program would compile if a default constructor A(){ } is added to class A explicitly.The program compiles, but it has a runtime error due to the conflict on the method name print.
What will be the output of the following code?class A { void method() { System.out.println("Class A"); }}class B extends A { void method() { super.method(); System.out.println("Class B"); }}public class Main { public static void main(String[] args) { B obj = new B(); obj.method(); }}
What will be the output of the following Java program?class A { int i; void display() { System.out.println(i); }}class B extends A { int j; void display() { System.out.println(j); }}class inheritance_demo { public static void main(String args[]) { B obj = new B(); obj.i = 1; obj.j = 2; obj.display(); }}Options02Compilation Error1
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.