Casting and dynamic vs static type in Java

Posted by XpdX on Stack Overflow See other posts from Stack Overflow or by XpdX
Published on 2010-04-20T04:55:45Z Indexed on 2010/04/20 5:03 UTC
Read the original article Hit count: 369

Filed under:

java

|

casting

|

typecasting

I'm learning about static vs dynamic types, and I am to the point of understanding it for the most part, but this case still eludes me.

If class B extends A, and I have:

A x = new B();

Is the following allowed?:

B y = x;

Or is explicit casting required?:

B y = (B)x;

Thanks!

© Stack Overflow or respective owner

Related posts about java

Tomcat 6: Access Control Exception?

as seen on Server Fault - Search for 'Server Fault'
I'm trying to setup a tomcat6 server, and I'm trying to match another setup someone else established. However, my deployment (default Ubuntu install) uses a policy.d/ directory structure, and the established server just uses a catalina.policy file. I've tried setting every entry in policy.d to match… >>> More
Problem in creation MDB Queue connection at Jboss StartUp

as seen on Stack Overflow - Search for 'Stack Overflow'
I am not able to create a Queue connection in JBOSS4.2.3GA Version & Java1.5, as I am using MDB as per the below details. I am putting this MDB in a jar file(named utsJar.jar) and copied it in deploy folder of JBOSS, In the test env. this MDB works well but in another env. [ env settings and… >>> More
failing to establish connection between Postgres db and gwt

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am using Postgres and gwt 2.0 for one of my applications. I am facing problem connecting to the database. When I try to connect it gives "ClassNotFoundException". Here is what I get when I try to connect to database: java.lang.ClassNotFoundException: org.postgresql.Driver at java.net… >>> More
failing to establish connection between postgre db and gwt

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, For i am using postgre and gwt 2.0 for one of my applications. I am facing problem connecting to the database. When i try to connect it gives "ClassNotFoundException". Here is what i get when i try to connect to database: java.lang.ClassNotFoundException: org.postgresql.Driver at java.net… >>> More
Migration and deployement problems JBoss 4.2.2.GA to JBoss 6.0.0.M2

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I'm trying to migrate an application running on JBoss 4.2.2.GA to JBoss 6.0.0.M2 I give you some log to explain my problem : boot.log : 2010-03-16 09:59:29,406 ERROR [org.jboss.system.server.profileservice.ProfileServiceBootstrap] (Thread-2) Failed to load profile: Summary of incomplete deployments… >>> More

Related posts about casting

Interface Casting vs. Class Casting

as seen on Stack Overflow - Search for 'Stack Overflow'
I've been led to believe that casting can, in certain circumstances, become a measurable hindrance on performance. This may be moreso the case when we start dealing with incoherent webs of nasty exception throwing\catching. Given that I wish to create more correct heuristics when it comes to programming… >>> More
Which casting technique is better for doing casting from upper class to lower class in C++

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi all, i want to cast from upper class pointer to lower class i.e from the base class pointer to derived class pointer. Should i use "Dynamic_cast" or "reinterpret_cast"? please advice me >>> More
Type Casting variables in PHP: Is there a practical example?

as seen on Programmers - Search for 'Programmers'
PHP, as most of us know, has weak typing. For those who don't, PHP.net says: PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. Love it or hate it, PHP re-casts variables on-the-fly… >>> More
Explicit casting doesn't work in default model binding

as seen on Stack Overflow - Search for 'Stack Overflow'
I am using ASP.NET MVC2 and Entity Framework. I am going to simplify the situation a little; hopefully it will make it clearer, not more confusing! I have a controller action to create address, and the country is a lookup table (in other words, there is a one-to-many relationship between Country… >>> More
PHP Equivalent of Java Type-Casting Solution

as seen on Stack Overflow - Search for 'Stack Overflow'
Since PHP has no custom-class type-casting, how would I go about doing the PHP equivalent of this Java code: CustomBaseObject cusBaseObject = cusBaseObjectDao.readCustomBaseObjectById(id); ((CustomChildObject) cusBaseObject).setChildAttribute1(value1); ((CustomChildObject) cusBaseObject).setChildAttribute2(value2); In… >>> More