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Because of the below reasons:
- Class implementations can change value of fields if they are not defined as final. Then they would become a part of the implementation. An interface is a pure specification without any implementation, hence they are final to prevent accidental modifications
- If they are static, then they belong to the interface, and not the object, nor the run-time type of the object.
- An interface provide a way for the client to interact with the object. If variables were not public, the implementing classes would not have access to them.
Hence variables in interfaces are public static and final
What else can I help you with?
Why can not define private and protected modifiers for variables in interface?
No. Interface variables are supposed to be public static final. Interfaces, like abstract classes, cannot be instantiated, so all variables in an interface must be static final ones. They are public because usually interfaces are used throughout an application, and this will ensure versatility.
What access attribute should static final variables have?
It should be public
How variable in interface is called?
All variables in an interface are by default public static and final and hence they are Constants.
What is difference in use between interfaces and abstract classes in java?
While neither abstract classes nor interfaces can be instantiated in Java, you can implement methods in abstract classes. Interfaces can only define methods; no code beyond a method header is allowed.
What is difference between abstract class and interface in core java give brief answer with example?
Differences:Abstract class can also contain method definitions but an interface can contain only declarationsAll variables in an interface are by default public static and final whereas in Abstract class it is notAn interface can be considered as a pure abstract class that contains no method implementations and contains only declarations.
What is public static final variable in java?
-Public to all - Static to access with Class Name - Final to change( constant and not alowed to change) Just use it along with class name. (As implied above, a 'public static final' variable in Java is what other languages would call a Constant. )
What is difference between interface and abstract in java?
While an abstract class can define both abstract and non-abstract methods, an interface can have only abstract methods. Another way interfaces differ from abstract classes is that interfaces have very little flexibility in how the methods and variables defined in the interface are declared. These rules are strict: • All interface methods are implicitly public and abstract. In other words, you do not need to actually type the public or abstract modifiers in the method declaration, but the method is still always public and abstract. (You can use any kind of modifiers in the Abstract class) • All variables defined in an interface must be public, static, and final-in other words, interfaces can declare only constants, not instance variables. • Interface methods must not be static. • Because interface methods are abstract, they cannot be marked final, strictfp, or native. (More on these modifiers later.) • An interface can extend one or more other interfaces. • An interface cannot extend anything but another interface. • An interface cannot implement another interface or class. • An interface must be declared with the keyword interface. You must remember that all interface methods are public and abstract regardless of what you see in the interface definition.
Can transient variables be declared as 'final' or 'static'?
Transient Variables are those that do not get serialized during the Serialization process. A Static variable is one that is mapped to the Class and is not mapped to any object instance and hence they would not get serialized. So, there should be no problem with declaring a transient variable as static. On the other hand, A final variable is one that's value cannot change. So if you declare a final variable as transient, it would get stored as null during serialization and when you try to de-serialize the variable, you will get errors because, the variable is final and you cannot assign values for it and it is saved as null during serialization. Result: Yes you can have static transient variables but not final transient variables.
Interface is used in java but not in C why?
The short answer: because C is not object-oriented. The reason for C++ not having interfaces is, that C++ supports multiple inheritance. Because C++ classes can be derived from more than one base class, so there is no need to have interfaces. In Java, each class has exactly one base class (except the class Object). With the help of interfaces it is possible implement a restricted (and more stable) form of multiple inheritance. Interfaces follow implicitly the following rules: * interfaces are abstract * each method is public abstract * each attribute is public static final
Can static variables be changed?
No, a static variable means that there is only one copy of that variable, and it is shared by all members of the class, or by all callers of a function.A variable that is read-only would be marked as const or final (depending on language).
Name a common Java library class that has public instance variables?
The Math class has public variables - defined as final, of course - for the mathematical constants PI and E.
What is the difference of interface and class?
A (concrete) class defines all his methods and can have any kind of instance variable and is declared with the 'class' keyword. Unlike an interface that doesn't implements any of his methods and his variables must be static and final. An interface is defined with the 'interface' keyword.//This is a classpublic class MyClass{public String name;private int age;public void myMethod(){//do something}}//This is a interfaceinterface MyInterface {public static final String name;public static final int age;public void myMethod(); // This method is not implemented}An other difference is that a class can be inheritance by other class but a interface must be implemented using the keyword 'implements'.interface Runnable(){void run();}public class MyOtherClass implements Runnable{public void run(){// insert interesting code here}}
