Why abstract method Graphics.drawString() can work without implementation?

Hi All,
Can anybody gives me a clear answer and a code example for this ???
J.Kathir

it won't work,
java.awt.Graphics is abstract class,
also overloaded drawString() methods are abstract.
You can expect the above code work in two scenarios.
Either Graphics should be a concrete class or
drawString() should be a static method.
Or....
You forgot an important one. That was mentioned before. So thanks for the completely valueless contribution.

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Why am i able to use abstract methods id they aren't yet implemented?

For example, why i can use this [http://docs.oracle.com/javase/7/docs/api/java/nio/CharBuffer.html#slice] if this is abstract?
Edited by: 947971 on 13-set-2012 10.38

947971 wrote:
Yes, but if CharBuffer has a method declared:
public abstract CharBuffer slice()So i can't use the method slice() because it's not implemented.
And why , indeed, i'm able to use it?Because it is implemented by the actual class being used. You can't instantiate abstract classes, so there is a subclass of CharBuffer which does implement the method.
If you take the interface Comparable, you see that it has an (implicitly)abstract method compareTo. A class that implements Comparable is Integer, so you can easily write:
Comparable<Integer> i = new Integer(100);
i.compareTo(new Integer(55));

[Solved] Browser that can work without mouse :)

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Why does this abstract class and method work without implement it?

hi,
I have seen many times that in some examples that there are objects made from abstract classes directly. However, in all books, manual and tutorials that I've read explain that we MUST implement those methods in a subclass.
An example of what I'm saying is the example code here . In a few words that example makes Channels (java.nio.channel) and does operations with them. My problem is in the class to make this channels, because they used the ServerSockeChannel class and socket() method directly despite they are abstracts.
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private static ByteChannel newChannel (int netPort)
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         return (fis.getChannel());
      } else {
//CONFLICT LINES
         ServerSocketChannel ssc = ServerSocketChannel.open(); //<--I have never thought do that!! Anyway, how it is static method may work.
         ssc.socket().bind (new InetSocketAddress (netPort)); //<--but here, this method (socket) is abstract. WHY RETURN A SOCKET???????? this mehod should be empty by default.
         System.out.print ("Waiting for connection on port "
            + netPort + "...");
         System.out.flush();
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   } I test this code and works fine. So why can it be??
Also, I read that the abstract classes can't have static methods. Is it true???
Please Help!!
PS: i have seen this kind of code many times. So i feel that I don't understand how its really the abstract methods are made.
PS2: I understand that obviously you don't do something like this: *"obj = new AbstractClass(); "*. I dont understand how it could be: ServerSocketChannel ssc = ServerSocketChannel.open(); and the compiler didn't warn.

molavec wrote:
ServerSocketChannel ssc = ServerSocketChannel.open(); //<--I have never thought do that!! Anyway, how it is static method may work.
The static method creates an instance of a class which extends ServerSocketChannel, but is actually another non-abstract class.I thought that, but reading the documentation I saw that about open() method:
Opens a server-socket channel.
The new channel is created by invoking the openServerSocketChannel method of the system-wide default SelectorProvider object.
The new channel's socket is initially unbound; it must be bound to a specific address via one of its socket's bind methods before connections can be accepted.
...and the problem is the same openServerSocketChannel is abstract, so i don't understand how it could return a ServerSocketChannel.There is a concrete implementation class that has implemented that method.
I guess that really the open() method use a SelectorProvider's subclase but it doesn't appear in the doc.It doesn't need to. First, you don't care about those implementation details, and second, you know that if the class is abstract, it must use some concrete subclass.
Ok, I speak Spanish by default (<-- this sounds like "I am a machine", ^_^' ). So, I didn't know how to say that the method would be {}. Is there a way to say that?? I recommendable for me to know, for the future questions o answers.Not sure what you're saying here. But the other respondent was trying to explain to you the difference between an abstract method and an empty method.
// abstract method
public abstract void foo();
// empty method
public void bar() {
Which class does extend ServerSocketChannel? I can not see it.It may be a package-private class or a private nested class. There's no need to document that specific implementation, since you never need to use it directly.

Anyone know of a Voice Translator that can work without WIFI? for travel

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Sony smartwatch can work without the phone?

hey guys!i dont know if i can post its here idk where but i have to know!
i bougt smratwatch today everythngs worked great(with galaxy S3)
now i dont have the phone near me just the watch
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As I understand the SmartWatch needs to be connected to the phone to be able to show date/time etc.
- Community Manager Sony Xperia Support Forum
If you're new to our forums make sure that you have read our Discussion guidelines.
If you want to get in touch with the local support team for your country please visit our contact page.

Why setValueExpression method for inputText not working properly

Hi,
JDev Ver : 11g 11.1.1.2.0
I have set value property of input text using setValueExpression method.
First time its working fine and setting value properly but when I set blank value using same setValueExpression method then input text automatically become read only.
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regards,
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Hi,
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Why wont my iphone's internet work without wifi?

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Method Graphics not entered, why?

Why the method Graphics(Graphics g) is not beeing entered?
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import java.awt.*;
import java.awt.event.*;
public class SwingApplication extends JFrame
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Why would it be? You never call the method, I think you mean to override paint. Change:
public void Graphics(Graphics g)to:
public void paint(Graphics g)That should be what you meant. Also, you shouldn't name your method Graphics, it's a class in the java.awt.

SAP Notes status can't be implemented?

Hi All
I would like to know, why few SAP notes status can't be implemented.
your view will be appreciated and will rewarded with <<removed by moderator>>.
Regards
Madhavi
Edited by: kishan P on Sep 1, 2010 1:03 PM

HI
Some SAP note can be implement manually and some are can be implement through the T-Code SNOTE
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nawa

Why can't there be a simple utility that shows me which device connected to my Airport is using how much of the bandwidth in a simple graphical or stats format without requiring me to be a level 10 Black Belt or Chuck Norris' paternal tooth fairy?

Why can't there be a simple utility that shows me which device connected to my Airport is using how much of the bandwidth in a simple graphical or stats format without requiring me to be a level 10 Black Belt or Chuck Norris' paternal tooth fairy?
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They are not overloading the Airport. They are overwhelming the capacity of your Internet connection.
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Mozilla can't find a valid PDF file to open in a browser, but Chrome or IE work without problem. Why?

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All is lowercase, no spelling error.
On Chrome, on the same computer, everything works fine.
I've also tested on Windows, still Chrome or IE work without problem.
Any ideas?

Thanks for your reply!
I've checked the link, and everything is set to its normal form in my browser.
Otherwise this particular case, the browser has no problems viewing PDF files,
but here, when I try to open the PDF (using HTML code, say,
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Not Found
The requested URL (the name) was not found on this server.

Static abstract methods - how can I avoid them?

Hi everybody,
just found out that java doesn't allow static abstract methods nor static methods in interfaces. Although I understand the reasons, I can't think of how to change my design to gain the required behavior without the need of static abstract methods.
Here's what I want to do and how my thoughts lead to static abstract methods:
ClassA provides access to native code (c-dll, using jna). The path to the dll can be set programmatically. Here's a draft of the class:
public ClassA {
   private static String path;
   public static void setRealtivePath(String path) {
      //check if path exists and is not null -> get absolute path
      setPath(path);
   public static void setPath(String absolutePath) {
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//code to provide access to native lib
}There is some more classes which provide access to different dlls (therefore the code for accessing the dlls differs from ClassA). Although this works, the setRelativePath method has to be implemented in each class. I thought it would be nice to put this method into a abstract super class that looks like this:
public abstract class superClass {
   public static void setRelativePath(String path) {
      //check if path exists and is not null -> get absolute path
      setPath(path);
   //force inherting class to implement a static method
   public static abstract void setPath(String absolutePath);
}thus simplifying ClassA and it's look-a-likes:
public ClassA {
   private static String path;
   @Override
   public static void setPath(String absolutePath) {
      this.path = path;
//code to provide access to native lib
}Since static abstract methods (and overriding static methods) is not allowed, this doesn't work.
I hope someone can catch my idea ;). Any suggestions how to do this in a nice clean way?
Thanks in advance,
Martin
Edited by: morty2 on Jul 22, 2009 2:57 AM

First of all, thanks a lot for your answer.
YoungWinston wrote:
Actually, you can "override" static methods (in that you can write the same method for both a subclass and a superclass, providing the superclass method isn't final); it's just that it doesn't work polymorphically. The "overriding" method masks the overridden one and the determination of what gets called is entirely down to the declared type.Yes, I know that. There's one problem: Your suggestion means that I simply have to drop the abstract modifier in the super classes setPath method. However, since the super class calls the setPath method (and not the inherting classes!) it will always be the super classes' method being called.
YoungWinston wrote:
Why are you so concerned with making everything static? Seems to me that the simplest solution would be to make all the contents instance-based.I want ClassA and it's look-a-likes to be set up properly at application start up, be accessible quite anytime and easily, they don't do anything themselves except for setting the path and calling into the native library which does the math. (Compareable to how you call e.g. Math.cos()). Therefore I don't think that an instance-based solution would be a better approach.
YoungWinston wrote:
Furthermore, you could make the class immutable; which might be a good thing - I'm not sure I'd want someone being able to change the pathname after I've >set up a class like this.Thanks for that!
PS: As mentioned in my first post, I do have a working solution. However, I'm really corious about finding a nicer and cleaner way to do it!
Martin

Why java does not force to declare atleast one abstract method

hi,
i can define an abstract class without declaring any abstract method in that class. But why wud i do this ? i mean when i have decided that a particular class should be inherited by other subclass and subclass should porvide implementation then there should be atleast one method in the abstract super class which requires implementation.
All i want to know is why java does not force to declare atleast one abstract method in abstract class.
there may be some situations where this restriction can create problem if it is like that then can anybody give some example.
manish

hi,
i didn't get u.
u r trying to say that i have an abstract class with
only static methods then my questions is why wud
declare such a class as 'abstract' class? because a
static method can't be abstract also. Even then if
somebody want to define such a class with only static
methods then compiler should force him to declare
atleast one abstract method which can be implemented
by subclass, because as i said before if sumbody
decide to define a class abstract then he wants that
it should be inhereted but as u r saying a class with
only static methods then it should not be an abstract
class it can be a simple class.there's no functional reason, really... actually, factory-like classes are often defined the way Ceci described
"abstract" only ensures that nobody can ever get an instance of that class (as a matter of fact, what would be the point of getting an instance, if no instance method exists ?)

Can i call non -abstract method in abstract class into a derived class?

Hi all,
Is it possible in java to call a non-abstract method in a abstact class from a class derived from it or this is not possible in java.
The following example will explain this Ques. in detail.
abstract class A
void amethod()
System.out.println(" I am in Base Class");
public class B extends A
void amethod()
System.out.println(" I am in Derived Class");
public static void main (String args[])
// How i code this part to call a method amathod() which will print "I am in Base Class
}

Ok, if you want to call a non-static method from a
static method, then you have to provide an object. In
this case it does not matter whether the method is in
an abstract base class or whatever. You simply cannot
(in any object oriented language, including C++ and
JAVA) call a nonstatic method without providing an
object, on which you will call the method.
To my solution with reflection: It also only works,
if you have an object. And: if you use
getDeclaredMethod, then invoke should not call B's
method, but A's. if you would use getMethod, then the
Method object returned would reflect to B's method.
The process of resolving overloaded methods is
performed during the getMethod call, not during the
invoke (at least AFAIK, please tell me, if I'm wrong).You are wrong....
class A {
    public void dummy() {
         System.out.println("Dymmy in A");
class B extends A {
     public void dummy() {
          System.out.println("Dymmy in B");
     public static void main(String[] args) throws Exception {
          A tmp = new B();
          Class clazz = A.class;
          Method method = clazz.getDeclaredMethod("dummy", null);
          method.invoke(tmp, null);
}Prints:
Dymmy in B
/Kaj

Why abstract method Graphics.drawString() can work without implementation?

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