201. Which are keywords in Java?
a) NULL
b) sizeof
c) friend
d) extends
e) synchronized
Ans : d and e
202. When must the main class and the file name coincide?
Ans :When class is declared public.
203. What are different modifiers?
Ans : public, private, protected, default, static, trancient, volatile, final, abstract.
204. What is an example of polymorphism?
Inner class
Anonymous classes
Method overloading
Method overriding
Ans : c
Packages and interface
205. What are packages ? what is use of packages ?
Ans :The package statement defines a name space in which classes are stored.If you omit the package, the classes are put into the default package.
Signature... package pkg;
Use: * It specifies to which package the classes defined in a file belongs to. * Package is both naming and a visibility control mechanism.
206. What is difference between importing "java.applet.Applet" and "java.applet.*;" ?
Ans :"java.applet.Applet" will import only the class Applet from the package java.applet
Where as "java.applet.*" will import all the classes from java.applet package.
207. What do you understand by package access specifier?
Ans : public: Anything declared as public can be accessed from anywhere
private: Anything declared in the private can’t be seen outside of its class.
default: It is visible to subclasses as well as to other classes in the same package.
208. What is interface? What is use of interface?
Ans : It is similar to class which may contain method’s signature only but not bodies.
Methods declared in interface are abstract methods. We can implement many interfaces on a class which support the multiple inheritance.
209. Is it is necessary to implement all methods in an interface?
Ans : Yes. All the methods have to be implemented.
210. Which is the default access modifier for an interface method?
Ans : public.