What Is Abstract Class
Jun 1, 2014I am just started to learn java and i am facing trouble learning abstract class.
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What Are Benefits Of Using Interface Plus Abstract Class Over Just Abstract Class
Oct 8, 2014What are the benefits of using an Interface plus an abstract class, over just an abstract class?
View Replies View RelatedConstructor In Abstract Class?
Jun 23, 2014Do we have constructor in abstract class? If we have then what is the use of it?
View Replies View RelatedWhen To Use Interface And Abstract Class
Apr 17, 2014I 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?
View Replies View RelatedReference Of Abstract Class
Aug 29, 2014I 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);
}}
Difference Between Abstract Class And Interface?
May 18, 2011Difference between Abstract class and Interface??
View Replies View RelatedWhy Can't Create Object Of Abstract Class
Jul 18, 2014Why we can't create object of abstract class ,when we can create its constructor?
View Replies View RelatedTemporary Object Of Abstract Class
Feb 21, 2015I 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] .....
Abstract Class Constructors Are Not Recommended
Aug 28, 2014in 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 }
Create Abstract Auto Class
Jul 23, 2014I'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]....
Can Create Object For Abstract Class
Oct 5, 2014Animal 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] ....
Writing Constructor In Abstract Class
Feb 4, 2015Below 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???
Interface Inside Abstract Class
Jul 8, 2015What 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] ....
Private Variable With Type Of Abstract Class
Oct 10, 2014I'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?
Performing Method On Instance Inside Abstract Class
Mar 12, 2015How 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?
Why Keyword Is Needed Infront Of Abstract Class Methods
Mar 7, 2014I 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]....
Why Super Classes Always Declared As Interfaces And Not Abstract Class
Dec 1, 2014While 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.
Swing/AWT/SWT :: Error At Class Name - Type JTextField Must Implement Inherited Abstract Method
Oct 27, 2014This 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] ......
What Programs Use Abstract Classes
Sep 15, 2014What programs use abstract classes?
View Replies View RelatedDifference Between Abstract And Inheritance
Dec 16, 2014I am new to java i dont understand the difference between the abstract and inheritance i mean we use the abstract class with extends with other class name ,even we do that same in the inheritance pls tell me main difference between abstract and inheritance...
View Replies View RelatedPolymorphism Possible Only When Superclass Is Abstract?
Jan 23, 2014I've a question regarding polymorphism.
Is polymorphism possible only when the superclass is abstract?
Abstract Method With No Implementation
Mar 6, 2014An abstract method is a method with no implementation. So would like to know what is the purpose of calling it if there is no implementation?
View Replies View RelatedAbstract Classes And Interfaces
Mar 29, 2014 I did research again....
interface:
methods - abstract, default, static ONLY(abstract methods have no body, while static and defaults do, right?)
fields - public, static, final ONLY
abstract class: a normal class, but has at least one abstract method
methods - all
i.e., static, non-static, abstract (can it have a default method?)
fields - all
i.e., public, protected, private / final, non-final / static, non-static
Interface And Abstract Classes In Java?
Jun 4, 2014why don't I define my methods in a class, rather than going a level up and declaring it first in an abstract class/interface? If the point is to have different implementations for different needs, then we have the option to override the methods.
View Replies View RelatedWhy Are Final And Abstract Called As Modifiers
Feb 8, 2015I just wanted to know that why are final and abstract called as modifiers ,what is the essence of calling them as modifiers since there are two types of modifiers access modifiers and non-access modifiers so final and abstract come under the second category ,so why are these called as modifiers?
View Replies View RelatedPlot Functions Using Abstract Methods
May 1, 2014Assignment 13 – Plot functions using abstract methods (Plot functions using abstract methods) Write an abstract class that draws the diagram for a function. The class is defined as follows:
Java Code:
public abstract class AbstractDrawFunction extends JPanel {
/** Polygon to hold the points */
private Polygon p = new Polygon();
protected AbstractDrawFunction() {
drawFunction();
[code].....
For each function, create a class that extends the AbstractDrawFunction class and implement the f method. Figure below displays the drawing for the first three functions.how to make the jframe to work so that I displays the panel
Java Code:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Graphics;
import java.awt.LayoutManager;
import java.awt.Polygon;
[code]....