Java syntax
part 38/46 · 86.7 KB total
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Interfaces can inherit from other interfaces just like classes. Unlike classes it is allowed to inherit from multiple interfaces. However, it is possible that several interfaces have a field with the same name, in which case it becomes a single ambiguous member, which cannot be accessed.
/* Class implementing this interface must implement methods of both
ActionListener and RequestListener */
interface EventListener extends ActionListener, RequestListener {
}
Default methods
Java SE 8 introduced default methods to interfaces which allows developers to add new methods to existing interfaces without breaking compatibility with the classes already implementing the interface. Unlike regular interface methods, default methods have a body which will get called in the case if the implementing class does not override it.
interface StringManipulator {
String extendString(String input);
// A method which is optional to implement
default String shortenString(String input) {
return input.substring(1);
}
}
// This is a valid class despite not implementing all the methods
class PartialStringManipulator implements StringManipulator {
@Override
public String extendString(String input) {
return input + " Extended";
}
}
Static methods
Static methods is another language feature introduced in Java SE 8. They behave in exactly the same way as in the classes.
interface StringUtils {
static String shortenByOneSymbol(String input) {
return input.substring(1);
}
}
StringUtils.shortenByOneSymbol("Test");
Private methods