What is encapsulation?

Correct Answer: Java uses sand box security model

Correct Answer: The diamond problem is an ambiguity that can occur when a class multiply inherits from two classes that both descend from a common super class

Correct Answer: Array is collection of same data type Array size is fixed, It cannot be expanded But ArrayList is a growable collection of objectsArrayList is a part of Collections Framework and can work with only objects

Correct Answer: An abstract class is defined with the keyword abstract Eg: public abstract class MyClass { }

Correct Answer: An abstract class is an incomplete class An abstract class is defined with the keyword abstract We cannot create an object of the abstract class because it is not complete It sets a behavioral protocol for all its child classes

Correct Answer: Inheritance is the ability to create new classes based on existing classes It is useful to reuse existing code

Correct Answer: Yes, we can In order to compile a java program, we don't require any main method But to execute a java program we must have a main in it (unless it is an applet or servlet) Because main is the starting point of a java program

Correct Answer: Overridden methods must have the same name, argument list, and return type (ie, they must have the exact signature of the method we are going to override, including return type) The overriding method cannot be less visible than the method it overrides( ie, a public method cannot be override to private) The overriding method may not throw any exceptions that may not be thrown by the overridden method

Correct Answer: Path and Classpath are operating system level environment variales Path is used define where the system can find the executables(exe) files and classpath is used to specify the location class files

Correct Answer: A method declared as final can't be overridden A sub-class can't have the same method signature with a different implementation