What is JVM ?
It is the heart of entire Java Program Execution process. It is responsible to take .class file & convert each byte code into machine Language. 

Features of JAVA ?
Simple - as concept of pointer is removed
Object Oriented - It uses concept of object and class
Distributed - Information can be distributed on various computers on a network.
Robust - Robust means strong(doesn't crash easily) because of exellent Handling Features & Memory Management.
Portability - yield same result on every machine,
High Performance - Because of JIT, both compiler & Interpreter works so fast.

What do you mean by Platform Independence?
Means we can write and compile the java code in one platform and execute the class file in any other supported platform.

DIfference between JDK and JVM?
JDK is Java Development Kit and JVM is Java Virtual Machine. JDK contains JVM and whole other tools for java development inside it. JVM converts bytecode to machine code and execute it on machine. There is no matching functionality between JDK and JVM.

What is the base class of all classes?
java.lang.Object

What are the access modifiers in JAVA?
Public: Public members are accessible everywhere outside the class. So any other program can read them and use them.
Private: class which are not accessible anywhere outside the class. Accessible only within the class by the menthods of that class. 
Protected: can be accessible outside a class but generally within the package.  
default: If no access specifier is written then Java Compiler uses a 'default' access specifier. It can be accessed outside the class but with same directory. 

Can a class be declared as private?
No, if we declare class as private then it is not available to Java Compiler & hence the compiler time errpor will occur.

What are package?
A java package is a directory that contain similar type of classes, interfaces and sub-packages. Package in java can be categorized in two form, built-in package and user-defined package. There are many built-in packages such as java, lang, awt, javax, swing, net, io, util, sql etc

What is Inheritance?
It creates new classes from existing classes so that the new classes will aquire all the features of the existing class. 
Exmaple: Parent producing children and children aquire qualities of parents.
Advantage: Reusibility of Code, we can create more useful class needed by the application.

What is the difference between superclass and subclass?
Superclass is the existing class from which the new class are derived while Subclass is the new class that inherits the properties and methods of Superclass. 

What is abstract Class?
Abstract classes are classes that contain one or more abstract methods. An abstract method is a method that is declared, but contains no implementation. Abstract classes may not be instantiated, and require subclasses to provide implementations for the abstract methods

What is Synchronization?
Synchronization is the mechanism that ensures that only one thread is accessing the resource at a time.

What is Applet?
Appletis a dynamic and interacive program that runs inside a web page displayed by a java capable browser.
or An applet is a small Internet-based program written in Java, a programming language for the Web, which can be downloaded by any computer.

What is Deadlock?
Deadlock describes a situation where two or more threads are blocked forever, waiting for each other. Deadlock occurs when multiple threads need the same locks but obtain them in different order.

What is life Cycle of an Applet?
init() : This method initializes the Applet and is invoked only once in the Applet life cycle. It helps to initialize variables and instantiate the objects and load the GUI of the applet,
start() : This method is invoked after the init() method. It starts the execution of Applet,
stop() : It stops the Applet execution. It’s invoked when the Applet stops or when the browser is minimized,
destroy() : This destroys the Applet and is also invoked only once when the active browser page containing the applet is closed.
paint() : This method helps to create Applet’s GUI such as  a colored background, drawing and writing.

What is JDBC?