Temporary Object Of Abstract Class
Feb 21, 2015
I am under the assumption that In the return statement of getReciprocal() method(of the following code), a temporary Number object is created to hold the result of the calculation.
My question is, Number is an abstract class and we are only able to create reference of an abstract class not an object. But then how a temp Number object is created and returned?
class Gen<T extends Number>{
T ob;
Gen(T ob){
this.ob = ob;
}
Number getReciprocal(){ // Number is abstract class
[Code] .....
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Jul 18, 2014
Why we can't create object of abstract class ,when we can create its constructor?
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Oct 5, 2014
Animal ob1=new Lion();
Here we create ob1 for Animal class or Lion class.
public abstract class Animal {
public abstract void eat();
public void breathe(){
[Code] ....
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Oct 8, 2014
What are the benefits of using an Interface plus an abstract class, over just an abstract class?
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Jun 1, 2014
I am just started to learn java and i am facing trouble learning abstract class.
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Jun 23, 2014
Do we have constructor in abstract class? If we have then what is the use of it?
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Apr 17, 2014
I know whats the interfaces and abstract class and also know that difference between interface and abstract class,but here my doubt is eventhough abstract class more advantage than the interface,then why should we use interfaces and when?
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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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May 18, 2011
Difference between Abstract class and Interface??
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Aug 28, 2014
in abstract class constructors are not recommended since we don't call it directly ...my doubt is below code is right or wrong...
3public abstract class Concept
4{
5 private String id;
6
7 protected Concept( String anId )
8 {
9 if ( anId == null )
10 {
11 throw new NullPointerException( "id must not be null" );
12 }
13
14 id = anId;
15 }
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Jul 23, 2014
I'm learning about abstract classes and I have to create an abstract auto class with make and price of a car, then two classes with a different type of car, and finally a main to use them. Everything seems to work and when I run it it's fine but I do get an error on the main that I'm not using the local variable buick1 and acura1.I'm curious because, while it runs for me, I want to make sure I'm doing it right and don't know of another way to do the output than this. I've put all four classes but the issue is on the last one (5 and 7).
public abstract class Auto
{
protected String makeCar;
protected double priceCar;
public Auto(String newMake)
{
makeCar = newMake;
[code]....
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Feb 4, 2015
Below Code
abstract class A
{
A(int a, int b)
{
}
}
If we can't create objects for abstract class, what is the need of writing constructor???
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Jul 8, 2015
What this interface inside that abstract class does. Looking for some examples to how can i use it ....
public abstract class Expression {
public abstract String toString();
public abstract SimpleExpression evaluate();
public void show() {
System.out.println(this + " = " + evaluate());
[Code] ....
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Oct 10, 2014
I've got an abstract class
public abstract class AbstractClass
{
//stuff
}
And a few classes that inherit from it
public class Class1 extends AbstractClass
{
//stuff
}
public class Class2 extends AbstractClass
{
//stuff
}
within another class I have a private variable with the type of the Abstract class, and within one of the methods I assign an object to the the variable like this:
public class Test
{
private AbstractClass temp;
public testMethod(){
Class1 anObject = new Class1();
temp = anObject;
}
}
Is this legal? Will temp become a Class1 object?
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Mar 12, 2015
How do I create an instance of a class in a method?
I am a bit rusty whenever I think of instances. I always think of main method and objects when I see instance which gets me confused on what to do when I am not in a main method. The example:
I have a abstract class, School, and inside School I have some methods that must preform some action on an instance. For example, there is a move() method that must move the instance of School. Another method named, personOld(), which returns whether or not an instance of School surpassed some determined age.
How do I do this and create this instance?
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Mar 7, 2014
I have a simple classes here one is interface and another one is abstract class when i try to compile them abstract class is givving compilation error.
public interface MyInterface{
public void getName();
public void getName(String s);
}
public class HelloWorld{}
abstract class SampleClass{
[code]....
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Dec 1, 2014
While reading the design patter book, i got one doubt ,There is a List an interface having sub classes ArrayList, LinkedList etc.,
Q1) My question is Why they declared the List as interface rather than Abstract class?
Q2) i read some site -
List l = new ArrayList(); Why it is GOOD line?
ArrayList l = new ArrayList() ; Why it is BAD line?
Answer required with detailed information for Q1 and Q2.
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Dec 13, 2014
Assuming that we have two classes B and C which inherit from class A. What is the best way to pass a parameter from an object of class B to an object of class C by the use of class A without using static variable and without defining a get function in B?
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Oct 27, 2014
This code is directly from Swing: I'm using Eclipse and keep getting an error on line 10 saying :
"The type JTextField must implement the inherited abstract method ActionListener.actionPerformed(ActionEvent)."
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
[Code] ......
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Oct 24, 2014
I wish to use the Request-Reply JMS pattern. The only part over here I am unsure of is the Temporary Queue and how to reuse it.
This is because the thread that creates the request must be able to map to a distinct reply and return back a response.
I am not sure how the reuse of a temporary queue fits this picture.
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May 18, 2015
I need to activate the setting 'Keep temporary files on my computer' (Java control panel/general/settings) on about 150 Windows 7 PCs in a Samba3-Environment (which does not have GPOs). We are running Java Version 8 Update 45 (build 1.8.0_45-b14) on all of the PCs. Is there a way to change this setting with the command line, a registry entry or somehow else?
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Apr 8, 2014
Suppose you have a generic Dog class of the pet type that implements a DogInterface of the pet type. What is the difference between;
DogInterface<pet> Rex = new Dog<pet>();
and
Dog<pet> Tye = new Dog<pet>();
In what situations might you want to use Rex instead of Tye?
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Mar 24, 2014
"You might wonder what happens when a static synchronized method is invoked, since a static method is associated with a class, not an object. In this case, the thread acquires the intrinsic lock for the Class object associated with the class. "What is a Class object associated with a class. Google search rather finds material about the Object class.
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Feb 4, 2015
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{
public void hello(){
System.out.println("hello");
}
}
class B extends A{
public void hello(){
//super.hello();
System.out.println("hello1");
[code]....
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Aug 28, 2014
can we pass private final class object to another class constructor?
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Apr 22, 2015
How to create object for "class B" and call the "function_B" from other different class D where class D has no connection with class A? Here is my program.
public class A(){
void print(){}
}
class B{
void function_B(){}
}
class C{
void function_C(){}
}
Here, A, B, C are in the same package. But class D is in different package.
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