Home | JSP | EJB | JDBC | Java Servlets | WAP  | Free JSP Hosting  | Spring Framework | Web Services | BioInformatics | Java Server Faces | Jboss 3.0 tutorial | Hibernate 3.0 | XML

Tutorial Categories: Ajax | Articles | JSP | Bioinformatics | Database | Free Books | Hibernate | J2EE | J2ME | Java | JavaScript | JDBC | JMS | Linux | MS Technology | PHP | RMI | Web-Services | Servlets | Struts | UML

Features

Struts Tutorials
*Stuts TOC
*Apache Struts Introduction
* Struts Controller
* Struts Action Class
* Struts ActionFrom Class
* Using Struts HTML Tags
*Struts Validator Framework    
*Client Side Address Validation    
*Struts Tiles
*tiles-defs.xml
*Struts DynaActionForm
*Struts File Upload
*Struts DataSource
*AGGREGATING ACTIONS
*Internationalization
Struts Resources
*Struts Books
*Struts Articles
*Struts Frameworks
*Struts IDE
*Struts Links
*Struts Presentations
*Struts Projects
*Struts Software
*Other Struts Tutorial
Visit Forum! Post Questions!
Jobs At RoseIndia.net!

Have tutorials?
Add your tutorial to our Java Resource and get tons of hits.

We offer free hosting for your tutorials. and exposure for thousands of readers. drop a mail
roseindia_net@yahoo.com
 
   

 
Join For Newsletter

Powered by groups.yahoo.com
Visit Group! Post Questions!

Core Java Interview Question Page 28

                         

Conversion Casting and Promotion

Question: What are wrapped classes

Answer: Wrapped classes are classes that allow primitive types to be accessed as objects.

Question: What are the four general cases for Conversion and Casting

Answer: 

Conversion of primitives
Casting of primitives
Conversion of object references
Casting of object references

Question: When can conversion happen

Answer: 

It can happen during

Assignment
Method call
Arithmetic promotion

Question: What are the rules for primitive assignment and method call conversion

Answer: 

A boolean can not be converted to any other type
A non Boolean can be converted to another non boolean type, if the conversion is widening conversion
A non Boolean cannot be converted to another non boolean type, if the conversion is narrowing conversion
See figure below for simplicity
assignment
Question: What are the rules for primitive arithmetic promotion conversion

Answer: 

For Unary operators :

If operant is byte, short or a char it is converted to an int
If it is any other type it is not converted

For binary operands :

If one of the operands is double, the other operand is converted to double
Else If one of the operands is float, the other operand is converted to float
Else If one of the operands is long, the other operand is converted to long
Else both the operands are converted to int

Question: What are the rules for casting primitive types

Answer: 

You can cast any non Boolean type to any other non boolean type
You cannot cast a boolean to any other type; you cannot cast any other type to a boolean

Question: What are the rules for object reference assignment and method call conversion

Answer: An interface type can only be converted to an interface type or to object. If the new type is an interface, it must be a superinterface of the old type. A class type can be converted to a class type or to an interface type. If converting to a class type the new type should be superclass of the old type. If converting to an interface type new type the old class must implement the interface. An array maybe converted to class object, to the interface cloneable, or to an array. Only an array of object references types may be converted to an array, and the old element type must be convertible to the new element.

Question: What are the rules for Object reference casting

Answer: Casting from Old types to Newtypes
Compile time rules

  • When both Oldtypes and Newtypes are classes, one should be subclass of the other
  • When both Oldtype ad Newtype are arrays, both arrays must contain reference types (not primitive), and it must be legal to cast an element of Oldtype to an element of Newtype
  • You can always cast between an interface and a non-final object

Runtime rules

  • If Newtype is a class. The class of the expression being converted must be Newtype or must inherit from Newtype
  • If NewType is an interface, the class of the expression being converted must implement Newtype

                         

Ask programming questions?

 

 

Add This Tutorial To:
  Del.icio.us   Digg   Google   Spurl   Blink   Furl   Simpy   Y! MyWeb 

Current Comments

0 comments so far (post your own) View All Comments Latest 10 Comments:
  JDO Tutorials
  EAI Articles
  Struts Tutorials
  Java Tutorials
  Java Certification

Tell A Friend
Your Friend Name

 

 
Browse all Java Tutorials
Java JSP Struts Servlets Hibernate XML
Ajax JDBC EJB MySQL JavaScript JSF
Maven2 Tutorial JEE5 Tutorial Java Threading Tutorial Photoshop Tutorials Linux Technology
Technology Revolutions Eclipse Spring Tutorial Bioinformatics Tutorials Tools SQL
 

Home | JSP | EJB | JDBC | Java Servlets | WAP  | Free JSP Hosting  | Search Engine | News Archive | Jboss 3.0 tutorial | Free Linux CD's | Forum | Blogs

About Us | Advertising On RoseIndia.net  | Site Map

India News

Send your comments, Suggestions or Queries regarding this site at roseindia_net@yahoo.com.

Copyright 2007. All rights reserved.

[an error occurred while processing this directive]