What is RMI and how it is useful?

Remote method invocation is called RMI.

One can work with remote object using RMI.

It gives a impression that you are working with a object that resides within your own JVM though it is somewhere.

The protocol used by RMI is RMI-IIOP

Define a Collection API.

The set of classes and interfaces supporting the operation on collections of objects is the Collection API.

Than the vectors, arrays, and hashtables if effectively replaces,these classes and interfaces are more flexible, more powerful, and more regular

class examples: HashSet, TreeMap, ArrayList, LinkedList,HashMap and TreeMap.

interface examples: Set,List ,Collection and Map.

How many forms of Polymorphism are there?

polymorphism exists in three different forms in Java:

  • Method overloading
  • Method overriding through inheritance
  • Method overriding through the Java interface

Define the wrapper classes in Java and name a few.

Wrapper class is wraps around the primitive data type. List of the primitive types and the corresponding wrapper classes:

Primitive Wrapper

boolean java.lang.Boolean

byte java.lang.Byte

char java.lang.Character

double java.lang.Double

float java.lang.Float

int java.lang.Integer

long java.lang.Long

short java.lang.Short

void java.lang.Void

Differentiate between JDK ,JRE & JVM

JDK stands for Java Development Kit. It is the most widely used Java Software Development Kit.

JRE stands for Java Runtime Environment. It is an implementation of the Java Virtual Machine which executes Java programs

JVM stands for Java Virtual Machine. It is an interpreter.