Home > Cannot Assign > Cannot Assign A Value To Final Variable Interface

Cannot Assign A Value To Final Variable Interface

I discovered it while learning depency injection. Though, this is not a good practice according to following excerpt: "Placing constants in an interface was a popular technique in the early days of Java, but now many consider it If it returns the String, the run() method in the thread will have to assign something to the function result, and you haven't solved the problem. What you need to do is put the variables you're sharing in a shared location. http://electrictricycle.net/cannot-assign/cannot-assign-a-value-to-final-variable-java-interface.html

Solution: Simply hang an abstract class between your interface and your implementation which only extends the abstract class like so: public interface IMyClass { void methodA(); String methodB(); Integer methodC(); } its value cannot be changed. I would say that this is not a bad practice - you are more likely to avoid a couple of bugs, save a few seconds for some readers. We do this every day when we specify a variable's type, of course: The language will ensure that values that are not of that type cannot be stored in that variable. http://stackoverflow.com/questions/4438228/the-final-field-cannot-be-assigned-for-an-interface

These variables are known as constants.Declaring a Variable as a ConstantIn declaring variables I showed that it’s easy to assign a value to a int variable: int numberOfHoursInADay = 24; We DeitelLimited preview - 2003All Book Search results » About the author(2006)A bio is not available for this author.Bibliographic informationTitleBeginning Java Objects: From Concepts to CodeThe expert's voice in JavaAuthorJacquie BarkerEdition2PublisherApress, 2006ISBN1430200367, Could I work as a Professor in Europe if I only speak English? final is not for variables, it's for constants. 0 Message Author Comment by:noparlpf2011-01-08 But if I take "final" off of them, then I get another error saying that they have

Far more comprehensive than mine. A class's public instance variables are part of its interface and there's no reason why they shouldn't be abstracted in a Java interface, just like instance methods. Since Java's black magic creates a copy of the environment in which the class is instantiated to pass variables to the inner class, you must declare them as final. For one thing, uninitialized variables are no longer any concern, because trying to use a final variable before it has been initialized will result in a compile error.

Interfaces should only contain constants if they're genuinely relevant to the rest of the interface, and they should use SHOUTY_CASE as per any other constant. Why are password boxes always blanked out when other sensitive data isn't? Privacy Policy Site Map Support Terms of Use Cookies help us deliver our services. http://stackoverflow.com/questions/10174050/cannot-assign-value-to-final-variable-in-java share|improve this answer edited Aug 9 '13 at 15:18 Hermes 32 answered Oct 22 '11 at 5:18 programmx10 1,202727 add a comment| up vote 0 down vote Here the reason why:

You create a new thread and use start() on it, and it looks like you're expecting this thread to modify responseBody1. This is my code here i have declared 'c' as "final int" but the line "c=Integer.parseInt(f.getText());" i am getting an error "cannot assign a value to a final variable". If you are forced to use a final, it's super easy : just do like so String newString = responseBody1; And then modify newString as you will edit: Just realized that Center trace between two pads Which movie series are referenced in XKCD comic 1568?

more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed Homepage This inner class, the ActionListener, persists past the time your function terminates - so it can't assign values to c, because c is local to the function. Declaring a variable final can serve as useful documentation that its value will not change and can help avoid programming errors. Join them; it only takes a minute: Sign up The final field cannot be assigned, for an interface up vote 7 down vote favorite I have a class Product and an

Is the English word "ikebana" a suitable translation for "華道"? Check This Out The variable is final, i.e. Join Now For immediate help use Live now! If 2 classes implement the same interface and you give both of them the right to change the value, conflict will occur in the current value of the var, which is

The code is as below: public interface Addable { static int count = 6; public int add(int i); } public class Impl implements Addable { @Override public int add(int i) { Once a final variable has been assigned, it always contains the same value. As habits go, it's not a bad one to develop. Source Plenty of titles dig into the Java language in massive detail, but this one takes the unique approach of stepping back and looking at fundamental object concepts first.

I tried removing the final modifier but it tells me I need to make it final, but when I do i get that error. share|improve this answer edited Nov 15 '14 at 10:23 answered Nov 14 '14 at 23:36 Gaktan 37828 What's the difference between final and static if you can't modify it? The quote was just elaborating on why such a constant would be static and final.

How do I reverse this javascript code?

If you are declaring fields in your class and not local variables in a method, then it's possible for multiple threads to access those fields at the same time. share|improve this answer answered Dec 14 '10 at 10:39 Jon Skeet 905k48965697492 1 What?! java interface share|improve this question edited Sep 9 '10 at 11:24 peSHIr 4,68312444 asked Mar 12 '10 at 5:47 Jothi 4,131144881 21 You shouldn't put any variables inside Interfaces. –cherouvim How to harness Jupiter's gravitational energy?

It is permitted to redundantly specify any or all of these modifiers for such fields. Without opening the PHB, is there a way to know if it's a particular printing? ex: "public final int mBars=4;" Additionally, I would recommend making all of your instance variable private instead of public. have a peek here Perhaps you should post a code example to demonstrate your solution. –ajb Nov 14 '14 at 23:50 @ajb I updated my anwser –Gaktan Nov 15 '14 at 10:24 add

share|improve this answer answered Dec 18 '15 at 10:05 Anssi 1,07775 add a comment| up vote 0 down vote (This is not a philosophical answer but more of a practical one). Covered by US Patent. Same reason. Please enter a valid email address.

Using a new variable instead of reusing an old one is how I can tell the compiler that trying to cover the complete universe of possibilities, and using final variables forces Because of their scope they already can be used by any method with in the class, but would not be susceptible to being altered by another class. The programmer that wrote this code knew as he was writing it that the values for the final variables should never be changed after assignment, and so made them final. Center trace between two pads How small could an animal be before it is consciously aware of the effects of quantum mechanics?

Will edit to explain. –Jon Skeet Dec 14 '10 at 10:40 @Jon final is the key issue here Check stackoverflow.com/questions/4438228/… –Jigar Joshi Dec 14 '10 at 10:43 1 The programmers may be using a tool that automatically add "final" where it can. Am I interrupting my husband's parenting? About Today Electronics & Gadgets Java You might also enjoy: Healthy Eating Health Tip of the Day Sign up There was an error.

Browse other questions tagged java interface or ask your own question. It's whenever I try to do something like labelThrow1.setOpaque(true); in clearButton. more hot questions question feed lang-java about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Synchronization is possible, but programming is hard enough already. ;-) So, if you just declare everything final out of habit, then many of your fields will be final and you'll spend

Everything enclosed between these delimiters is treated as a comment and is therefore ignored by the Java compiler, no matter how many lines the comment spans.‎Appears in 4 books from 2003-2005MorePage Is adding the ‘tbl’ prefix to table names really a problem? When an instance of the class is instantiated, you will be able to access its instance variable. –pyrocrasty May 9 at 6:49 Java allows static methods with bodies to Subscribe to our monthly newsletter for tech news and trends Membership How it Works Gigs Live Careers Plans and Pricing For Business Become an Expert Resource Center About Us Who We

Can I get a dual entry Schengen visa for tourism purpose for me and my wife? To make them into constants just add the final keyword to their declaration.Where to Declare ConstantsAs with normal variables you want to limit the scope of constants to where they are Any attempt to assign a new value to a final variable after assignment will result in a compiler error.