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Java Class Q&A » interface » abstract class 3 

1. interfaces and abstract classes    forums.oracle.com

The main purpose of constructor is to initialize the instance variables to give them default values when an object for a class is created . So on this notion abstract class is still a class but has its some methods which is abstract or just marked abstract , so that the other classes can extend it (provide concrete implementation of it) ...

2. When we will go for an abstract class and when we will go for an interface?    forums.oracle.com

jwenting wrote: with experience and the insight it brings, you will know which to use when. Without it, it can't be explained. More often than not there's no X OR Y anyway. It's fortunate that there are posters here who possess the insight and experience necessary to explain this. The principal differences between an abstract class and an interface are, 1. ...

3. interface and abstract class    forums.oracle.com

4. interface and abstract class    forums.oracle.com

5. abstract class and interface    forums.oracle.com

Both has differences Abstract class It has constructor It has both abstract method and implementation method. Interface there is no constructor in interface it is not in object hierarchy you should declare public static final variables only in interface and method should be abstract when you want to declare group of constants, you can go for interface.

6. Abstract class and interface    forums.oracle.com

Another difference : Members of an abstract class have default access rights by default ... however, the members of an interface are always public by default ! However, the major difference lies in the fact that, with an abstract class you can provide the end user with some default functionality + the ability to enhance the features of the class by ...

7. what is the difference between an interface and an abstract class?    forums.oracle.com

so whats the difference ??!! i know i may sound stupid but im kindda a beginner in java technology and this question is killing me ....so please can someone explain it to me in simple words !!! ....what i know is that you IMPLEMENT an interface class (in which you can implement many interface classes) while you can only EXTEND one ...

8. interface & abstract class    forums.oracle.com

9. what is an interface & abstract class ?    forums.oracle.com

=> An interface can also include constant declarations. =>All methods in interfaces are abstract.(methods = series of statements that perform some repeated task.) =============================================================================== Abstract class. ****************** =>An abstract class = is a class that is declared abstract. => An abstract class that contains one or more abstract methods, (abstract methods = methods with no implementation.) =>An abstract class is a ...

10. abstract classes and interfaces?    forums.oracle.com

An interface is a class that defines the names of the methods you must use. For example if you are working on part of a project for a company and they have specific names that they want for there method such as checkInventory replaceInventory calcPrice They could define these in an interface, then in your class you would implement the interface ...

11. Abstract classes and Interfaces    forums.oracle.com

12. abstract class and interface    forums.oracle.com

Hi, This is ramana, I got a doubt 1. I have one interface interface Intabs { abstract void method1(); abstract void method2(); abstract void method(); } 2. Iam trying to convert that interface into abstract class like below interface Intabs { abstract void method1(); abstract void method2(); abstract void method(); } 3. Again iam trying to extend that abstract class into ...

13. Abstract Class & Interface    forums.oracle.com

A second goal is to design a class hierarchy that makes it possible for computers to play the game, as well as human users. Thus, for a given two-player game, it should be possible for two humans to play each other, or for two computers to play each other, or for a human to play against a computer. This design goal ...

14. Why Interfaces and Abstract classes in JAVA    forums.oracle.com

It kind of weirds me out to think of the kids growing up that have never lived in a world without the internet. I wonder if people felt the same way about cars and refrigerators and such. That's always the case, isn't it? I'm in my forties and I remember how excited I was when my high school got a primitive ...

15. Diffrence between Abstract Class and Interface?    forums.oracle.com

I don't know how many times I've replied to these kinds of questions. And its equallly frustrating each time you realize the OP doesn't care and you'll never get an acknowledgement that he's even bothered to read your reply. So I've started asking an initial test question to see if there's a genuine interest at the other end. It usually isn't, ...

17. abstract class and interface    forums.oracle.com

18. interface vs abstract class    forums.oracle.com

19. When to use Abstract class and Interface?    forums.oracle.com

RajivGuna wrote: Then what is the purpose of interface? Please explain me when to use an interface? The one thing that you can do with interfaces is have completely separate classes implement the same interface. Say for example i have a Foo interface. I could have a Bar class that implements the interface and a completely unrelated Baz class that also ...

21. documentation formats for interfaces, classes, abstract classes    forums.oracle.com

I am writing docs and want to make sure it conforms to best practices. Here is what I am doing: interfaces = [italics, not bold] classes = [not italics, bold] abstract classes = [italics, bold] I am most unsure of abstract classes? That is important to me, so please help me get this straight. thanks.

24. Newbie confused ... abstract class, interface, implementation ....    forums.oracle.com

This abstract class provides default implementations for most of the methods in the TableModel interface. It takes care of the management of listeners and provides some conveniences for generating TableModelEvents and dispatching them to the listeners. To create a concrete TableModel as a subclass of AbstractTableModel you need only provide implementations for the following three methods:

25. Interfaces and Abstract classes    forums.oracle.com

27. Abstract Classes & Interface Classes    forums.oracle.com

Dear members of the Sun Community My studies are progressing and just 1 period ago we started doing Object-Orinted Programming in Java and I must say I'm quite fond of it. It's become quite clear that OOP is an important aspect of Programming and just can't be missed. We've learned about Inheritance, Polymorfism, Mutators, Inspectors, Uses-Relationships and everything else however now ...

28. which is faster abstract class or interface in terms of speed    forums.oracle.com

RGEO wrote: actualy i have an option between abstract and interface, so thats why i have this question. i know that in context of speed both are aprox. equal.But i realy want to know which is good. What has speed got to do with "good"? I mean, let's say one is a fraction of a millisecond faster than the other. But ...

29. difference between interface and abstract class    forums.oracle.com

Requirement : we should have 2 objects Dog and Cat with some of their related features. Considering this , immediately it will strike in ur mind that i need to have 2 classes named " DOG" and "CAT". Now u will think that some of the features of the DOG & CAT can be common . ( for eg: -- say ...

30. abstract class and interface use    forums.oracle.com

31. A question to choose between interface and abstract class    forums.oracle.com

Hi all, I have two options to choose from, whether to use an abstract class or an interface. Now before you jump up and say that please google this answer i have a set of conditions which are: 1) In my interface or abstract class i would be using only one or more abstract methods and no fields or variables. 2) ...

32. Abstract Class with all abstract methods is same as Interface ?.    forums.oracle.com

Actually my doubt is : Interface is full of abstract methods right == I will have all the methods in abstract class itself ... Then why they introduced interface . There are some more reasons i think expect Multiple Inheratance. Please tell other reasons... Actually this question is asked on interview ....

33. Abstract class and Interface class    forums.oracle.com

Pasting your exact subject into google gives [http://www.google.com/search?q=Abstract+class+and+Interface+class] I'm sure after 10 minutes perusing some of those pages, you'll have a basic idea. An additional 20-30 minutes and maybe a couple more google searches for things that come up during that reading should give you a pretty solid understanding. At that point, if some particular issue is not clear to you, ...

34. About abstract class VS interface class    forums.oracle.com

35. Interface and Abstract Class    forums.oracle.com

36. Diff between Abstract class and interface - is this a difference    forums.oracle.com

This is quite a common topic thats discussed in any java forums . I would like to confirm if asked about the differences , can I say the following?. Abstract class can (or not ) have methods in it and it has no use in instantiating it since it has no meaning in instantiation. It has to be inherited for use ...

37. Abstract Class Vs Interfaces    forums.oracle.com

The answer for your question can take several pages =) So read documentation or find some article by google is the best solution. Briefly: * Both of abstract classes and interfaces can not be instantiated. * Both of them declares methods, which must be implemented by theirs concrete subclasses (but it is possible to create interfaces without any methods and abstract ...

38. Interfaces and Abstract Classes    forums.oracle.com

In situations like these I have used two solutions: 1. A separate Map of image to integer that the painter keeps. Then you don't need to hold a z score in your objects 2. Composition: Create a composite object that takes an image (or whatever) and a z score that is just mostly or wholly used inside your graphics package BTW, ...

39. abstract class cannot be override from an interface class    forums.oracle.com

We're going to need a lot more information about about your actual circumstance in order to offer any intelligent advise... Don't be shy, do tell. As a general rule of thumb you don't *uck with existing class heirarchies... if you do have to *uck with existing class heirarchies (either because they're fundamentally broken, or no longer fulfill your requirements) then you ...

40. Problems with Abstract classes and Interfaces    forums.oracle.com

Okay, so here's the gist of my issue. public abstract class A implements Comparable {...public into compareTo(){...}...} public class B extends A {... public int compareTo(){...}...} public class C extends A {... public int compareTo(){...}...} I get errors when I attempt to compile. Netbeans and whatever compiler is running on the university computers both say that Class B and C are ...

44. Abstract Class vs Interface    forums.oracle.com

45. Interfaces, Abstract Classes & Polymorphism    forums.oracle.com

Where in that assignment does it mention interfaces, abstract classes, or polymorphism? One potential place to use one of them (either an interface or abstract class) would be to have a Crypt [interface/abstract class] that provides an input field and a method that provides the decoding, and then have your Encrypt and Decrypt class each [implement/extend] that [interface/abstract class].

46. Make abstract class with interface.    forums.oracle.com

47. Interfaces and abstract classes    forums.oracle.com

Hello, I am confused between an Interface and an abstract class. I would cite an example: I consider various shape objects esp. square, rectangle etc. and consider a common behavior area which I need to determine for each of these shapes. Should I consider an Interface or an abstract class and why?

49. Interface Vs abstract Class    forums.oracle.com

Let say that an abstract class has all abstract functions and someone use it instead of interface. What are the disadvantage and advantages? I know one that he cannot do multiple inheritance, hence he cannot extends abstract class and use any other parent Class. However, I wish to know more disadvantage/advantages. Looking forward for your input. -- PS: I know interface ...

50. when to use interface and abstract class?    forums.oracle.com

I have been search resources that explan when to use interface or abstract class. there are some docs, but they are kind of vague to me. It would be great if someone gives me a practical and easy example about this. Use extends when the superclass represents a classification IS-A relationship. This is when the superclass constitutes a concept the subclasses ...

51. Interface or a Abstract Class is more useful    forums.oracle.com

52. Abstract class and interface    forums.oracle.com

53. Abstract class Vs Interface    forums.oracle.com

Can any one say when to use a abstract class and when Interface. This is a very basic question and the answer lies in the basic differences between the two. Abstract classes have atleast one method abstract and interfaces have all abstract methods. If you are developing some application in which any entity can have more than one implementation, it is ...

54. Which is faster,interface or abstract class?    forums.oracle.com

Say what now? There's a difference? Dam i gotta go hit the books again, maybe my apps can perform better (jk), There's been allota new post about performce in this forum, i gotta feeling you are all in the same class. Tell your prof to bugger off wow the ****** represent the word "b u g g e r" and it ...

55. where we use abstract class & interface...    forums.oracle.com

oo design usually follows the pattern of abstract design and concreate implementation. if the object you are designing has an abstract notion, use an abstract class to describe that notion, and then extend it for more concreate notions. for example, if you want to describe the notion of fruit, make it an abstract class, then you can extend it for more ...

57. Which one is to use between Interface and Abstract Class    forums.oracle.com

=> An interface can also include constant declarations. =>All methods in interfaces are abstract.(methods = series of statements that perform some repeated task.) ==================================================== 2- Abstract class. ******************** =>An abstract class = is a class that is declared abstract. => An abstract class that contains one or more abstract methods, (abstract methods = methods with no implementation.) =>An abstract class is ...

59. difference between interface and abstract class    forums.oracle.com

An interface is a 100% abstract class, which means it doesn't contain any code, just method names and signatures. You use abstract classes when you want some code to be shared among the inheritors. The advantage with interface is that a class can implement as many interfaces as you like, while it can only extend one (abstract) class. So, you use ...

60. Interfaces vs abstract classes    forums.oracle.com

I tend to use abstract classes when I want to have some default behaviour already implemented, and I only want to override a few methods. I find this useful when the abstract class acts as a superclass to several different classes that share similar behaviour. I cannot provide default behaviour in an interface, I can choose to implement more than one ...

61. Which is faster,interface or abstract class?    forums.oracle.com

Yes but 'class' is shorter than 'interface'. OTOH 'abstract class' is longer, and you can omit 'public abstract' in interfaces ... Seriously folks I don't know why this issue is even taught or asked. It's an implementation detail, miles down in the guts of the JVM, that has had little significance since about the time HotSpot came in in the previous ...

62. Abstract Class & Interface?    forums.oracle.com

somewhere i came across an explanation for this. Below is that. Abstract Class: 1) Have executable methods and abstract methods. 2) Can only subclass one abstract class. 3) Can have instance variables, constructors and any visibility: public, private, protected, none Interface: 1) Have no implementation code. All methods are abstract. 2) A class can implement any number of interfaces. 3) Cannot ...

63. Abstract Classes VS Interfaces    forums.oracle.com

64. abstract class and Interface    forums.oracle.com

abstract public void methodI(); // must be implemented at subclasses abstract public void methodII(); public void methodAvaiableForAllClasses() { do something; // you can call methodI and methodII here } } abstract classes also lets you define global variables to be used (i heard its faster than interfaces too, but I don't know enough about it to confirm). Interfaces in the other ...

66. what is the main difference between interface and abstract class    forums.oracle.com

Difference between interface and abstract: All the methods declared inside interface should be abstract, and there is no need to use the key word abstract for those method, but in case of abstract class at least one method should be abstract, most importantly u have to use the abstract key word for that method, besides that it may contain concrete methods. ...

67. Hi all,Interface vs Abstract class    forums.oracle.com

Interface class is used to contain methods that is to be defined by children classes. And abstract class, even though you can have all methods being abstract, but normally I would use this class for situation such as implement methods that are general enough to be used by the children classes and left others being abstract to be implemented by children ...

68. Difference between Interface and Abstract Class    forums.oracle.com

well atom, how many protons do you have... one... that's inheritance. how many chemical reactions do you support? as many as required... that's the BunsenBurner, and the SoreBum interfaces. An abstract class can (and frequently does) contain implementation. An interface cannot contain implementation. Java doesn't support multiple inheritance (like C++)... so you can extend exactly 0 or 1 classes (which isn't ...

69. Some questions related to "Prefer interfaces to abstract classes"    forums.oracle.com

Yes, one of the reasons interfaces are better is that you can only extend one class, but implement many interfaces. Say you have a concrete class that should "implement" two different types. If those types were defined as abstract classes, you could only use one type. You could implement both types if they were interfaces though.

70. Difference b/w Abstract Class and Interface    forums.oracle.com

71. Interfaces Vs Abstract Classes    forums.oracle.com

do your own homework. had you just asked for the differences, you would probably have gotten an answer, but you've just dumped your homework on the forum and said "do this for me" which we won't search the forums for this, it's asked almost every day. but those homework questions? that's your own problem

72. ABSTRACT CLASS vs INTERFACE ?    forums.oracle.com

hi all, can anybody help me. if i have an abstract class (full of abstract method definitions) and an interface(having same definitions). Now the question is in which situation we go for an ABSTRACT CLASS with full of abstract method definitions and in which situation we go for an INTERFACE. and other differences between ABSTRACT CLASSES and INTERFACES except Multiple Inheritence ...

74. What is the main difference b/w interface and abstract class    forums.oracle.com

Hi., 1. All the methods declared inside an interface are abstract whereas abstract class must have at least one abstract method and others may concrete or abstract. 2. In abstract class, key word abstract must be used for the methods whereas interface we need not use that keyword for methods. 3. Abstract class must have subclasses whereas interface cant have subclasses. ...

75. Why would you ever use an interface instead of an abstract class?    forums.oracle.com

Can somebody tell me, then, why Joe Doe would want to use an interface over an abstract class? The main reason is a limitation in the Java inheritance model namely that you can inherit one class only but as many interfaces as you want. This can be characterized as: single inheritance of implementation but multiple inheritance of type. The latter is ...

76. interfaces and abstract classes    forums.oracle.com

hi, Can anyone help me regarding the difference between interfaces and abstract classes. What is the advantage of interface over abstract classes and viceversa. Obout the possibities of multple inheritance I know. I found allmost all people are talking some external answers. Why an abstract class cant we do it with concrete class. regards, Jayaprasad Viswanathan

77. Interfaces are slower than Abstract class    forums.oracle.com

Interfaces are slower than abstract class .Because interfaces requires extra indirection to find the corresponding method in the actual class.Can some explain me this indirection process and how it is done in case of abstract class.And also some one can give tell me where to use interface and abstract class with live example.

78. Interfaces and Abstract Classes    forums.oracle.com

I know you can use Abstract classes/interfaces to create method signatures that must be implemented in the extending/implementing class, but is there a way to create variable or constructor signatures that the extending/implementing class has to implement for themselves also? Variables don't have implementations, so no, not really. I assume you realise that a public field will be available to all ...

79. interface and abstract class    forums.oracle.com

The difference is 1. on abstract class you can define the implementation of the methods, which is not the case with interface 2. When implementing interface, user must implement all the method declared on the interface. Also this is not the case with abstract class 3. To use abstract class, use keyword "extends" 4. To use interface, use keyword "implements" About ...

80. Abstract classes and Interfaces    forums.oracle.com

Why would you use these? Why not make a concrete class and extend them? I see why JAVA doesn't use mutiple inheritance but I don't see how allowing interfaces correctes that, after all what happens if two interfaces implemented by one class have two fully defined methods with the same signature but differant outputs? I tryed googleing this but just got ...

81. usage of interface and abstract class    forums.oracle.com

If you want to define a pure abstract type, use an interface. If you want to provide a partial implementation for some type--such as default implementations for methods that can be done without regard to the specific implementation--use an abstract class. And quite often you'll use both. The interface defines the type, and the abstract class implements the interface, providing some ...

82. Abstract Class Implementing an Interface    forums.oracle.com

I wonder why the Verb2 class compiles. I expected a compilation error, and here is my reasoning. The package-level "isSpelled" method in the Verb2 class is fine. However, class Verb2 implements interface Word, and class Verb2 does not appear to fulfill the interface contract. That is, the "isSpelled" method in class Verb2 has a different method signature than the interface Word ...

83. I don't understand the concepts of Abstract Classes and Interfaces    forums.oracle.com

I have read so many articles about Abstract Classes and Interfaces, but still I cannot understand their real use. One of the reasons would be code re-use or something along those boundaries, although this doesn't make sense to me, because an interface only defines the methods, so if I were to change a method name in the Interface class, I would ...

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