Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true?

JAVA Interfaces and Abstract Classes
Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true?

The method numberOfStudent() in class School must have a body.

You must add a return statement in method numberOfStudent().

Class School must be defined abstract.

The keywords public and abstract cannot be used together.

The method numberOfStudent() in class School must have a body.

You must add a return statement in method numberOfStudent().

Class School must be defined abstract.

The keywords public and abstract cannot be used together.

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JAVA Interfaces and Abstract Classes
Given the following piece of code:public interface Guard{ void doYourJob();}abstract public class Dog implements Guard{ }which of the following statements is correct?

This code will not compile, because method doYourJob() in interface Guard must be defined abstract.

This code will not compile, because class Dog must implement method doYourJob() from interface Guard.

This code will compile without any errors.

This code will not compile, because in the declaration of class Dog we must use the keyword extends instead of implements.

This code will not compile, because method doYourJob() in interface Guard must be defined abstract.

This code will not compile, because class Dog must implement method doYourJob() from interface Guard.

This code will compile without any errors.

This code will not compile, because in the declaration of class Dog we must use the keyword extends instead of implements.

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JAVA Interfaces and Abstract Classes
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();

1 and 3

3 and 4

2 and 3

2 and 4

1 and 2

1 and 3

3 and 4

2 and 3

2 and 4

1 and 2

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JAVA Interfaces and Abstract Classes
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?

2

1

4

None of these

3

2

1

4

None of these

3

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JAVA Interfaces and Abstract Classes
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); }}

None of these

Compilation error due to line 2

Successful run and print 37

Compilation error due to line 1

Runtime error

None of these

Compilation error due to line 2

Successful run and print 37

Compilation error due to line 1

Runtime error

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JAVA Interfaces and Abstract Classes
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"); }}

b is an instance of

Nothing.

b is an instance of

b is an instance of A followed by b is an instance of

b is an instance of

Nothing.

b is an instance of

b is an instance of A followed by b is an instance of

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JAVA Interfaces and Abstract Classes

JAVA Interfaces and Abstract Classes Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true?

JAVA Interfaces and Abstract Classes Given the following piece of code:public interface Guard{ void doYourJob();}abstract public class Dog implements Guard{ }which of the following statements is correct?

JAVA Interfaces and Abstract Classes 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();

JAVA Interfaces and Abstract Classes 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?

JAVA Interfaces and Abstract Classes
Given the following piece of code:public class School{ public abstract double numberOfStudent();}which of the following statements is true?

JAVA Interfaces and Abstract Classes
Given the following piece of code:public interface Guard{ void doYourJob();}abstract public class Dog implements Guard{ }which of the following statements is correct?

JAVA Interfaces and Abstract Classes
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();

JAVA Interfaces and Abstract Classes
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?