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) }}

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

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JAVA Interfaces and Abstract Classes
What is the output for the below code ?interface A{ public void printValue();}1. public class Test{2. public static void main (String[] args){3. A a1 = new A(){4. public void printValue(){5. System.out.println("A");6. }7. };8. a1.printValue();9. }10. }

null
A
None of these
Compilation fails due to an error on line 3
Compilation fails due to an error on line 8

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JAVA Interfaces and Abstract Classes
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();}}

will print Class Two method
compiles fine but print nothing
None of these
Compilation Error
will print Class One method

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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 A followed by b is an instance of
b is an instance of
Nothing.
b is an instance of

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

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

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