Interfaces

Question 1

To define (declare) an interface class we use the keyword?

Answer 1

Interface

Question 2

interfaces imposed at ? (Compile or runtime)

Answer 2

compile time

Question 3

if a class implements an interface, all methods must be ?

Answer 3

overridden

Question 4

A class can implement … number of interfaces?

Answer 4

many

Question 5

a class can extend how many classes ?

Answer 5

at most one

Question 6

interfaces can be in form of ?

Answer 6

fields or methods

Question 7

data members of interface are

Answer 7

public static final

Question 8

all methods of interface are

Answer 8

public abstract

Question 9

interface is implemented using the keyword

Answer 9

implements

Question 10

does an interface need a constructor? why?

Answer 10

no, because it can’t be instantiated

Question 11

can interfaces inherit each other? how?

Answer 11

yes, by using extends

Question 12

java supports multiple inheritance in form of?

Answer 12

in form of interfaces

Question 13

all methods in an interface must be overridden, unless?

Answer 13

they are declared abstract

Question 14

if a superclass implements an interface, all subclasses?

Answer 14

also implement it

Question 15

common interfaces in java?

Answer 15

1. comparable (compareTo())
2. comparator (compare(), equals())
3. serializable
4. cloneable

Question 16

compareTo return values are…

Answer 16

-ve, 0 , +ve

Question 17

while compareTo return value means equals

Answer 17

0

Question 18

which (abstract or interface) can have abstract and non abstract methods?

Answer 18

abstract class

Question 19

which (abstract or interface) can have static, non static, final and non final variables?

Answer 19

abstract

Question 20

which (abstract or interface) provides implementation of interface ?

Answer 20

abstract

Question 21

which (abstract or interface) only extends interface classes?

Answer 21

interfaces

Question 22

abstract classes are inherited using keyword?

Answer 22

extends

Question 23

interface are inherited using the keyword?

Answer 23

implements

Question 24

interface classes members can have modifiers of

Answer 24

public only