java constants class vs interface
An Interface in Java is a reference type similar to a class that can contain constants as fieldsvariables abstract methods and nested types. Most advice on Internet has the following opinions.
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Do not use Interfaces for constants.
. It is the same as the final variables. Interface for constants. By default the fields declared in interface are public static final.
This is only a minor advantage. Java Enums vs Constants. Interface is declared using interface keyword.
How do you define and use constants in Java. A class may implement numerous interfaces. Interface can have only abstract methods.
An interface can have abstract methods and static constants. An interface is abstract so that it cant provide any code. First never create a single class or interface for dumping all of your constants.
Before JDK 8. In addition to the logistics of maintaining the Constants class itself were also inviting other maintainability problems by encouraging too much interdependency with this one global constants class and various other parts of our application. Variables declared in a Java interface are by default final.
I know it is tempting but after 1 or 2 years that constant file will become very messy and unreadable. Instead if a variable has a very close relationship with a class it is better to put the constant variable in that class. Java best practice Interface - subclasses and constants.
We can also achieve multiple inheritance in java using interface. Fields are by default public static and final whereas methods are by default public and abstract whether we declare or not. In the case where a couple of classes implements an interface and those classes have a couple of constants in common but no functions were should I put this constant.
DataFromSensors that I use to hide the. Interface can inherit only an inteface. 2 Fields in interface should not be preferred.
If the constant string belongs to the class and you only need the string value keep in the class that uses it. Public static final String VALUE2 bar. 1 Both the constants have same meaning.
An abstract class may contain non-final variables. If a class implements such an interface then the class can refer to those constants without a qualifying class name. A class can implement an interface.
From Java 8 it can have default and static methods also. For Situation 2. That a class uses some constants internally is an.
An abstract class can have abstract and non-abstract methods. I have this interface. A class inherits only one abstract class.
Joshua Bloch in his famous book Effective Java talks about it in greater detail. We cannot define the method body in the interface. Public final class MyValues private MyValues No need to instantiate the class we can hide its constructor public static final String VALUE1 foo.
The static import feature should always be considered as a replacement for this practice. Use a final class and define a private constructor to hide the public one. Where a constant is un-modifiable and have only one copy through out the program.
From Java 8 it can have default and static methods also. Its possible to place widely used constants in an interface. This is only a minor advantage.
A class can extend only one abstract class while a class can implement multiple interfaces. A class can inherit another class using extends keyword and implement an interface. An abstract class can give complete default code which should be overridden.
Dont use an Interface for situation 1. On a more technical side the Java compiler places the value of the constant into referencing variables in the classes in. Interface can not implement an interface it can extend an interface.
Ive had this problem a couple of times. Show activity on this post. Declare public static final for constants in a class.
Constants are usually defined in upper cases as a rule. A class implements an interface. Apply the use of Enums to represent those constants as a object.
It is of no consequence to the users of a class that the class implements a constant interface. One can then use the constant in another class using ClassNameCONSTANT_NAME. The most common way to define a constant is in a class and using public static final.
As mentioned in the link above as Constant Interface Anti-pattern. You cannot use access modifiers for the method properties etc. The constant interface pattern is a poor use of interfaces.
Abstract class vs Interface. A class is declared using class keyword. Until unless you are very much confident that another interface wont have field with same name.
Use of Access modifiers.
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