![]() ![]() This restriction is designed to detect, at compile time, most circular or otherwise malformed initializations.Īs shown in an example in §8.3.2.3, the fact that initialization code is unrestricted allows examples to be constructed where the value of a class variable can be observed when it still has its initial default value, before its initializing expression is evaluated, but such examples are rare in practice. The static initializers and class variable initializers are executed in textual order, and may not refer to class variables declared in the class whose declarations appear textually after the use, even though these class variables are in scope (§8.3.2.3). The intent here is that a class or interface type has a set of initializers that put it in a consistent state, and that this state is the first state that is observed by other classes. Here is an extract from the JLS3 - Sec 12.4.1 Order of execution of the initializers is one of the things to consider here. Having them could only mean more work for the compiler? ![]() I think we can safely say that because of the above, the static blocks are not required in an interface. ![]() The following two styles must be functionally equivalent ( not really sure on this one - not sure if inlining works with both, but it must be an implementation detail ) though the first one must be more concise and readable. For the former, in an interface the static variables are already also final variables. So they don't apply.Ī static block is generally used to initialize variables that should be initialized only once or to call a static method. ![]() We can redefine the Walkable interface to include the letThemWalk() method.Could this be one another way to put it? Just my reasoning - if you think it's incorrect, please point out.įirst we only have instance method declarations in an interface for obvious reasons - implementation is deferred to an implementing class that declares to keep the contract. The above declaration of the Player interface can be rewritten as follows without changing its meaning:Ībstract method declarations in an interface may include parameters, a return type, and a throws clause.īoolean play(int account) throws AccountNotFoundException īoolean forward(double amount) throws InsufficientBalanceException Ībstract methods from an interface are implemented by classes that implement the interface, and classes override them to provide an implementation.Īn abstract method in an interface cannot be declared final.Ī class may declare the overridden method of an interface final indicating that the subclasses cannot override the method.įrom Java 8, we can have static methods in interfaces.Ī static method contains the static modifier and are implicitly public. Use of the abstract and public keywords in a method declaration in an interface is redundant. The Player interface is a specification for an audio/video player.Ī real player, for example, a DVD player, will provide the concrete implementation of the specification by implementing all four methods of the Player interface. The following code declares an interface named Player: The body of the abstract method is always represented by a semicolon, not by a pair of braces. All method declarations in an interface are implicitly abstract and public unless they are declared static or default.Īn abstract method in an interface does not have an implementation. ![]()
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