Question 1 of 25
Hints left: 3
Q1
Suppose A is an abstract class, B is a concrete subclass of A, and both A and B have a default constructor. Which of the following is correct? 1. A a = new A(); 2. A a = new B(); 3. B b = new A(); 4. B b = new B();
Q2
Which of the following class definitions defines a legal abstract class?
Q3
In Java, declaring a class abstract is useful
Q4
Which of the following statements regarding abstract classes are true?
Q5
What is the result of the following code snippet? abstract class MyAbstract { MyAbstract() { System.out.println("Constructor"); } } class MyClass extends MyAbstract { public static void main(String[] args) { MyClass obj = new MyClass(); } }
Q6
Determine output of the following code. interface A { } class C { } class D extends C { } class B extends D implements A { } public class Test extends Thread{ public static void main(String[] args){ B b = new B(); if (b instanceof A) System.out.println("b is an instance of A"); if (b instanceof C) System.out.println("b is an instance of C"); } }
Q7
What is the result of the following code snippet? abstract class MyAbstract { private void myMethod() { System.out.println("Private Method"); } } class MyClass extends MyAbstract { public static void main(String[] args) { MyClass obj = new MyClass(); obj.myMethod(); } }
Q8
In Java, can an abstract class have default methods with implementations?
Q9
Given the following piece of code: public interface Guard{ void doYourJob(); } abstract public class Dog implements Guard{ } which of the following statements is correct?
Q10
In Java, can an abstract class have constructors?
Q11
In Java, can a class implement an interface and extend an abstract class simultaneously?
Q12
What will be the output? interface A{ public void method(); } class One{ public void method(){ System.out.println("Class One method"); } } class Two extends One implements A{ public void method(){ System.out.println("Class Two method"); } } public class Test extends Two{ public static void main(String[] args){ A a = new Two(); a.method(); } }
Q13
What will happen after compiling this program code? abstract class MyClass{ //line 1 private int a, b; public void call(int a, int b){ this.a = a; this.b = b; System.out.print(a+b); } } public class Test{ public static void main(String args[]){ MyClass m = new MyClass(); //line 2 m.call(12,25); } }
Q14
Which of the following declares an abstract method in an abstract Java class?
Q15
What is the purpose of the "final" keyword in Java?
Q16
In Java, can an abstract class have static methods with implementations?
Q17
In Java, can an abstract class have private methods with implementations?
Q18
Which two of the following are legal declarations for abstract classes and interfaces? 1. final abstract class Test {} 2. public static interface Test {} 3. final public class Test {} 4. protected abstract class Test {} 5. protected interface Test {} 6. abstract public class Test {}
Q19
interface Test{ int p = 10; //line 1 public int q = 20; //line 2 public static int r = 30; //line 3 public static final int s = 40; //line 4 } Which of the above line will give compilation error?
Q20
What is the result of the following code snippet? abstract class MyAbstract { static void myMethod() { System.out.println("Static Method"); } } class MyClass extends MyAbstract { public static void main(String[] args) { MyAbstract.myMethod(); } }
Q21
interface Base{ boolean m1 (); byte m2(short s); } which two code fragments will compile? 1. interface Base2 implements Base {} 2. abstract class Class2 extends Base { public boolean m1(){ return true; }} 3. abstract class Class2 implements Base {} 4. abstract class Class2 implements Base { public boolean m1(){ return (7 > 4); }} 5. abstract class Class2 implements Base { protected boolean m1(){ return (5 > 7) }}
Q22
What is the result of the following code snippet? interface MyInterface { static void myMethod() { System.out.println("Static Method"); } } class MyClass implements MyInterface { public static void main(String[] args) { MyInterface.myMethod(); } }
Q23
Which of the following is a correct interface?
Q24
In Java, can an interface have static methods with implementations?
Q25
Given the following piece of code: public class School{ public abstract double numberOfStudent(); } which of the following statements is true?