What Programs Use Abstract Classes
Sep 15, 2014What programs use abstract classes?
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Abstract 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 RelatedHow Does Inheritance Work With Abstract Classes
Nov 19, 2014I am writing small pieces of code to make sure I understand Java basics and I have the following.
package teams1;
public abstract class Team1{
private String sport = new String();
public abstract String getSport();
public abstract void setSport();
}
import teams1.*;
[Code] .....
It doesn't compile because sport is private in the super class, but I thought FootballTeam1 would inherit it's own copy of sport because it is extending Team1.
Abstract Classes And Access Modifiers
Jan 21, 2015I'm having difficulty understanding this small piece of code:
package food;
public abstract class Fruit {
private String color;
private String tasteType;
public void setColor(String color) {
this.color = color;
}
public abstract void setTasteType(String taste);
}
The above is an abstract class which describes the basic structure that every fruit should "extend".
The below is a concrete subclass of the Fruit class called Apple.
import food.Fruit;
class Apple extends Fruit {
public void setTasteType(String taste) {
tasteType = taste;
}
}
Also do note that the two pieces of code are in different packages!
Upon compiling the Apple class I get the following error:
Apple.java:4: error: tasteType has private access in Fruit
tasteType = taste;
^
What I don't understand is this: I've given a non-abstract implementation to the "setTasteType" method in the Apple class and clearly setTasteType should have the authority to modify the private instance variables of Fruit. But it turns out I'm wrong.
Interface / Abstract Classes And Loading Array
Oct 20, 2014I am new to Java, and last week had an assignment to create a shopping list. I made it so that I have one class use a ProductData class to load an array of objects (description, price, priority). This week I need to take that program and change it so that it includes an Interface and Abstract Class. I need to also split one class up into at least 2 others.
I am having trouble getting my thoughts together and figuring out what to put in the interface and what to put in the abstract class. I'm thinking that it might be best to split up the ProductData class up into 3 different classes: description, price, and priority. Then have an interface with a print method. Each of those 3 classes will implement the interface.
As for the abstract class, have the price and priority extend the abstract class. The abstract class will be at the same level as the interface and contain the set and get methods. Right now they are of 2 different data types: int, double. Should I make both of them Double, and then use a method to change the priority to an int?
Should price and priority inherit from description, or should they all be at the same level? I am thinking that they should be at the same level because they all describe the item in the array.
My most confusing part is that I have no clue at all on how I can load that array when each object is split up in a different class. My professor went over ArayLists last week, and we can now use them if we want, but the assignment doesn't explicitly say that we should change it to an Array List. Where does the constructor for the ProductData() go? Do I split it up into 3 different constructors?
Error Using Abstract Classes - Cannot Find Symbol
Feb 2, 2014I am stuck. It seems like I have done everything by the book but I keep getting the same error: cannot find symbol. The error is specifically addressing lines 9, 10, and 11 in the Alien class file. All that is supposed to happen is an output of information for the two types of aliens.
Java Code:
import javax.swing.*;
public class CreateAliens
{
public static void main (String[] args)
{
Martian aMartian = new Martian();
Jupiterian aJupiterian = new Jupiterian();
JOptionPane.showMessageDialog
(null, "
[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.
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 RelatedUse IDE When Writing Programs
Mar 27, 2014I was wondering if you use an IDE when writing programs?Can you use J frame when using command line or is it just used with an IDE and do you go into framing in the book?I have taken programming classes and I am still stuck.
View Replies View RelatedChanging Values In Different Programs?
May 20, 2014I'd like to make a simple cheat for an old game that's offline... It has no type of anti-cheat and I'd like to make a program that changes how much money you have... I think the first thing I have to do is get the data address or something like that by using cheat engine... How do I do that? After that how do I start using that info in my program and then send back a new value? Are there any classes that I should be importing and what methods do I use to do this?
View Replies View RelatedPrograms To Display Only Odd Numbers Between 1 And 15
Nov 16, 2014I have a programs to write which is to display only the odd numbers between 1 and 15 and the code i use it is not display what i was expecting it to but instead it looping 15 times and at the end it says that the odd number is 15 or 1. where or what have i entered wrong. it supposed to display only the odd numbers between 1 and 15here is the code that I write.
Scanner input = new Scanner (System.in);
int i, num=0, count = 0, count_odd = 0, oddnum = 0;
for(i=1; i<=15; i++) {
System.out.println("Please enter number");
num = input.nextInt();
}
[Code]....
Resize Window To See Programs
Jan 21, 2014Whenever I make something in Swing, I always need to resize the window for me to see the graphics on the window. I have been told to use the pack() method on it, which I have, but the problem with it is that it just sets the window to a minimal size, only displaying the x + and -.For one of the "games" I made, it at first didn't work until resize, then I added a repaint() after the constructor and it worked for me, but when my friends download it they cannot see it.
View Replies View RelatedRunning Programs Through Java
Mar 30, 2014I've been playing around with this for about an hour.
Java Code:
Runtime runTime = Runtime.getRuntime();
try {
Process process = runTime.exec("notepad");
} catch (IOException e) {
e.printStackTrace();
} mh_sh_highlight_all('java');
So that works. Notepad will open.
However, I'm trying to get other programs to open. Specifically, this program: C:Octave3.2.4_gcc-4.4.0inoctave-3.2.4.exe...However, using that in place of notepad doesn't work. I'm assuming that there is some sort of system variable that explains why simply typing "notepad" works? As if you type notepad into the run box, notepad will open. Soo does that snippet work by going through some sort of system variables?How would I go about opening other programs, such as the one I referenced above.
Program That Will Allow Programs Only At Certain Time
Sep 25, 2014So I am making a program that will allow programs only at a certain time and i'm not sure how I would set the time for the program.
View Replies View RelatedHow To Structure Simple Java Programs
May 8, 2015how to structure simple programs (i.e. one-method algorithms for a simple purpose). There are a few different ways that I have been doing it, but I want to be consistent. Should I put both the one-method algorithm (e.g. a factorial function) and the main method that executes the algorithm into the same class and then export it to an executable .jar file for use? Or should I create one class for the algorithm and another for the main method that executes the algorithm? In addition, is there any reason that I should out these classes in a package before I export it?
As another similar question, if I have constructed two distinct classes with two separate purposes, and they are both used in the construction of a single program, then would it be best to just put the main method in a third, separate class or should I put it in one of the two classes?
How To Compile And Run Java Programs Using JDK And JCreator
Jan 26, 2014How do I set the class path, the path, compile and run java programs using jdk and jcreator?
View Replies View RelatedRunning Java Programs From Command Prompt
Dec 17, 2011My PC runs on Windows XP. When I try to run a java program (written using NetBeans) from the command prompt, the program opens in NotePad but does not run.This is what I have been typing at the command prompt:
C:javahellosrchelloHello.java
The above is the correct path to the Java file on my PC.how to run the program from the command prompt or perhaps link me to a tutorial that explains it?
What Is Abstract Class
Jun 1, 2014I am just started to learn java and i am facing trouble learning 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 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?
Reference 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);
}}
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 RelatedHow To Call Classes Within Other Classes
Apr 18, 2014How do you call classes within other classes? Or can you only call classes through the main?
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