In Java, even if we do not specify the public with the method name, all methods in the interface are public. In addition, even if we did not mention it in the field name, the data field is public static final. Therefore, the data field must be initialized.

Consider the following example. Even without a specifier, x is public static final by default, and foo() is public.

In Java, interfaces are used to define a set of methods that a class can implement. These methods are used to specify the behavior of an object. Each method in an interface can have a different access specifier, which determines who can access the method.

There are three access specifiers in Java: public, protected, and private. In an interface, all methods are implicitly public. This means that any class that implements the interface can access the methods in the interface. However, if a method in the interface is marked as private, it cannot be accessed by any class that implements the interface.

The protected access specifier cannot be used in an interface, as it is used to restrict access to members of a class to the class and its subclasses. Since interfaces cannot be instantiated, there is no class hierarchy that can define subclasses of an interface.

In summary, the access specifier of methods in interfaces is implicitly public. This means that any class that implements the interface can access the methods in the interface. If a method in the interface is marked as private, it cannot be accessed by any class that implements the interface. The protected access specifier cannot be used in an interface.