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 keywords public and abstract cannot be used together.
Class School must be defined abstract.
You must add a return statement in method numberOfStudent().
The method numberOfStudent() in class School must have a body.

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JAVA Interfaces and Abstract Classes
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) }}

2 and 3
3 and 4
4 and 5
1 and 3
1 and 2

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JAVA Interfaces and Abstract Classes
In Java, declaring a class abstract is useful

When it doesn't make sense to have objects of that class.
When default implementations of some methods are not desirable.
When it makes sense to have objects of that class.
To force developers to extend the class not to use its capabilities.
To prevent developers from further extending the class.

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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 in the declaration of class Dog we must use the keyword extends instead of implements.
This code will not compile, because class Dog must implement method doYourJob() from interface Guard.
This code will compile without any errors.

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