Cannot Pass By Reference?
Aug 25, 2014
I'm fairly new to Java, I'm very experienced with C++ and C# in which you can pass by reference - extremely useful. Take for example this bit of code in C#:
class MyClass
{
public MyClass(int i)
{
m_i = i;
}
public int m_i;
[Code] ...
Just at the end of this program x.m_i will be equal to 8. As far as I can see this is not possible in Java: you can't pass a double by reference, using a Double will kick in the autoboxing so that won't work either. The only "solution" in Java would be to pass in a double[] (of length 1) or to make a wrapper class, both nasty solutions because a user may want to just hold a double as a member of their class just as I have, for reasons such as not allocating more memory for a class and generally not being bloated.
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Aug 27, 2014
if there is a possibility to use the pass by reference technique in java like in C++.URL....
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Mar 11, 2014
i'm having issues with pass by reference between remote EJB method calls. Below is what i'm trying to do. The EJB method calls are made using remote (EJBObject) interface.
insertEmployeeRecord(Employee employee) {
employeeEJB.insertEmployee(employee);
empDetailsEJB.insertEmpDetails(employee);
}
insertEmployee(Employee employee)
[Code] ....
All the EJBs have below configuration in the weblogic-ejb-jar.xml file.
<enable-call-by-reference>true</enable-call-by-reference>
I'm using Weblogic server 10.3.0.4 and JDK160_21.
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Jan 27, 2014
I am doing a Junit test case, but I keep having issues with AssertEquals ( object expected, object actual). I don't know how to reference the other actual object so that it can compare to the expected.
public void add (Distance d) throws CustomException
{
//I can also convert feet to inches and add all inches together and then divided inches to feet and inches
Distance result = new Distance();
int newFeet = this.feet + d.getFeet();
int newInches = this.inches + d.getInches();
if(newInches > 11)
{
newFeet = newFeet + (newInches/12);
[Code]...
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Jan 24, 2015
I don't really know what this means and it is sending an error when I try to run my program I am trying to set the x and y value (Int x and int y) to setVisible false at a specific time in my game but it keeps sending the error that int is not a reference type.
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Mar 15, 2015
I am making an MVC program and I am not allowed to put the action listeners in the view class. I was able to get one button working fine but since I am unable to reference them I cannot give them both individual responses.
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Controller {
HobbyList model;
ListView view;
[code]....
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Apr 17, 2014
public class {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double[] numbers = new double[10];
System.out.println("Enter " + numbers.length + "numbers");
for (int i = 0; i < numbers.length; i++) {
numbers[i] = input.nextDouble();
[Code] .....
I am trying to reference the input "numbers[i]" to my mean method, how do i do that?
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Nov 12, 2014
I know in C++ It's possible to pass by reference but what about java?
For example, can i pass the address of a health variable into a Ninja class and then
Since Ninja inherits from an enemy class pass the health into the enemy class and within there have a function that returns that same health address and takes 5 from the health returning 95.
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Aug 29, 2014
I passed my abstract class private final reference to another concrete class and I used abstract class reference as parameter to that concrete class constructor and in my main method and null to that parameter then only that program executes correctly...i placing my code below ..if there is any error tell me where is error occurring then i will check my code...i think my code is right but little bit doubt abstract class concept.
{
}
class concept1 extends concept
{
private final concept parent;
public concept1(concept aparent)
{
parent=aparent;
System.out.println(parent);
}
public static void main(String args[])
{
//concept p=new concept1(null);
concept c=new concept1(null);
}}
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Mar 29, 2014
When I write a statement such as:
myType x;
This means that x is a reference to objects of type, "myType" and no memory has been set aside for an instance of this object. I think it's true that x also has the starting memory address of this object.
What I feel uncertain about is if x is telling the JVM(?) where it can find the starting address of this object, why do we care about the type that x is?
i.e., if we assign x to an object totally unrelated to this type then the compiler would complain - correct? If so, how come, since all x is doing is telling the JVM(?) where to find your object (via the address it contains).
I suppose all, hy a reference has a type associated with it if all the reference does is point you to the object?
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May 17, 2014
I am currently learning Java basic concepts and this is a very simple code which produces error depending on the way I write. It is as follows:
package testPackage;
interface ArrayInsideClassShock {
}
class Check{
ArrayInsideClassShock var[]; //Error line
var= new ArrayInsideClassShock[10];
}
Error in eclipse:Syntax error on token ";", , expected
But if I write it as:
package testPackage;
interface ArrayInsideClassShock {
}
class Check{
ArrayInsideClassShock var[]=new ArrayInsideClassShock[10];
}
It doesn't show any error.
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Feb 15, 2010
what these mean with examples..
1. A reference variable can be of only one type and once declared, that type can never be changed(although the object it references can change)
2. A reference is a varaible ,so it can be reassigned to other objects(unless the reference is declared final)
3. A reference variable's type determines the methods that can be invoked on the object the variable is referencing.
4. A reference variable can refer to any object of the same type as the declared reference , or - it can refer to any subtype of the declared type.
5. A reference variable can be declared as a class type or an interface type. If the variable is declared as an interface type, it can reference any object of any class that implements the interface.
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Jan 23, 2014
I don't understand why following code when executed returns false
String s1= " string".trim();
if(s1 == "string"){
System.out.println("true");
}
else{
System.out.println("false");
}
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Jan 29, 2014
How can i check the reference that is not duplicate and date format is DDDCCYYnnnnnnn, CC must be 20 and YY must not be less than the current year, nnnnnnn is the sequetial number of the file and to complete the 7 numeric characters, zero's must be populated in front of the number. DDD must be a valid reporting entity code. there must not be a duplicate. Code I try
private boolean test-date()
{
String s_Ref = this.transactionFile.getsReference();
boolean flag = true;
if(!isValidPattern(s_Ref, "[0-9]{14}"))
[Code] ....
The reference number is like 201401030234509
If there is duplicate show error code 105
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Feb 28, 2015
I am unable to understand the meaning of this sentence "final reference variables must be initialized before the constructor completes.",What is trying to imply?
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Oct 30, 2014
I have started working on a little project in my free time. It is just a simple text rpg that runs in a counsel window. I have 5 files each file contains 1 class.
public class SomnusCharacter {
private String gender = "";
private int age = 0;
private String race = "";
private int level = 0;
private int xp = 0;
[Code] ....
The chain of events right now is:
1. MainMenu is run
2. If user inputs n CreateCharactor is run
3. User inputs name, age, ect in SomnusCharacter object made in CreateCharacter
4. Intro (just rough demo for testing purposes) is run
5. If user inputs m Menu is run
6. Menu calls and prints out all the information from the object made in CreateCharacter
Step 6 is where I am having my problems. How can I reference (lets say the SomnusCharacter object made is called player) player from my Menu class? I know that if I made a new character that it would just create another SomunsCharacter object with the default values again.
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May 22, 2014
I read somewhere : "Java use clone() method of Object class to copy content of one object to the other. The problem will arrive if the Class that needs to be copied also contains reference to the other object."Not able to understand the second line.
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Sep 30, 2014
How are methods invoked on the `bird` parameter?
next.xhtml:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
[Code] ....
`MyQueueBean` is intended to give out a bird once only, to exactly one end-user. Because it's application scoped, and not session scoped, getting attributes directly from the bean would give inconsistent results.
The birds application is from Facelets Essentials Guide to JavaServer Faces View Definition Framework: [URL] ....
how is the variable passed to the file? Once it's passed, how is it referenced?
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May 18, 2015
Is there a short term that means: "using an object reference with the datatype of a supertype to refer to an object with the datatype of a subtype"?
Saying "polymorphic reference" doesn't seem to be specific enough because ALL references other than those with the Object datatype are polymorphic. I saw one post that referred to these reference variables as a "supertype reference." In the absence of any other (more official) term, I may just use that term because calling a reference a "supertype reference" implies that there is a subtype. It sure beats what I was thinking about using: "sub-as-super." Which, when the inevitable mispronunciations occur, would lead to all kinds of off-color jokes.
Is there an "official" term that all of the dozens of Java books I have read seem to have missed? Or does everyone stumble along, spelling things out with a nearly sentence-long phrase.
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May 10, 2014
Is there a way to forward the text child of an anchor tag to its hyper reference?
For example, suppose I have an HTML file:
<a href = "ABC.jsp">SomeText</a>
Is there a way to send text 'SomeText' to ABC.jsp so it can be processed?
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Aug 14, 2014
I have just started to work on Java EE and I am not able to put the refrence of css and javascript in jsp page.
My senario is below: I have created script file inside myJavaScript Folder like Web Container-> myJavaScript ->Home.js. Similarlly for css:Web Container-> myCss ->Home.css.
My Jsp page palced inside Like: Web Container-> Home ->Home.jsp.
How to give the reference of js and css file in my Home.jsp page.
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Jun 15, 2014
Check out the following basic code (assume that dog has a method called bark):
Dog d = new Dog();
Object o = d;
o.bark(); // error
But why? Isn't o just a pointer to a memory address which has the dog object? If so, why can't the compiler see that the object has a method called bark? Or, to ask the question another way, why is Java designed to check the object reference to see if the method exists instead of the object itself?
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Feb 21, 2015
getting the value of the selected radio button. My jsp file has the below code:
<h:selectOneRadio label="Requests" value="#{user.a_request}" layout="pageDirection">
<td ><f:selectItem itemLabel="Forward Request to A" itemValue="A"/></td>
<td ><f:selectItem itemLabel="Forward Request to B" itemValue="B"/></td>
</h:selectOneRadio>
Any my java bean has:
package test;
import java.io.Serializable;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import java.util.Map;
[code]...
in the value of the radio button "{#user.a_request}", it is producing an error that the reference "user" is not found.
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May 14, 2015
If a method is overridden but you use a polymorphic (supertype) reference to refer to the subtype object with the overriding method, the compiler assumes you're calling the supertype version of the method.
is this true? maybe i'm misunderstanding it, but i thought the JVM looks at the object at run time and checks the object type. the context of the quote is about checked exceptions, but it seems like the statement should stand regardless of context. but this doesn't back up my experience. for example:
public class Test{
public void print(){
System.out.println("Super");
} public static void main(String[] args){
Test t = new SubTest();
[Code] ....
Will invoke the subclass method. like i said, maybe i'm missing something.
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May 6, 2014
I'm trying to design a website that will require users to register and login before they use it. In order to keep things separate, I was thinking it might be useful to create a single web archive that just handles the user signup and login. That way I could work on my other web archive apps independently and have them just check to see if the user has logged in and posted a token somewhere, and if not redirect to the login webpage.
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May 21, 2014
I got a project at my university , and we are working with JBoss with the free version WildFly .And also with Java EE.
Now the application is a simple game of Battle Ships or sinking ships to be honest i am not sure as to how the game is actually called.
Registering a user and saving his or her information is not hard using a Stateless java bean , to save the data in the database.
I have a Stateful java bean for every user , the bean is created on the server side after the user succeeds in logging in to the game.
This bean is used mainly for sending an invite from one user to another , to log out the user and everything else that is needed for the user.
The main problem that i encountered here is that JBoss dose not let me have a reference on my frame inside of the bean.
This makes things hard because i would need to use a Timer to ask the bean every second or so if there is an invite from someone , and i would need to save all of the invites .
This was the only thing i could think of .And also implementing the game it self , the communication between users would be complicated more so than i think its needed.
Then my professor said that i could make a service on the clients side in witch i would have a reference of the JFrame , and i could send this service to the java bean and using this service i could get access to the JFrame making things faster.
This would make things a lot easier.For the invite and for the game itself too.
My professor explained that JBoss or WildFly is based on RMI , and he said also that i would need to set up the registry on the server side .But i got lost because i was not sure as to what should i search for .
We are using an older version of WildFly not the newest but one version older , CR1 i think.
And we are also using JPA in the Dynamic web project , server .
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