I know that an interface is like a 100% pure abstract class. So, it can't have method implementation in it. But, I saw a strange code. Can anyone explain it?
Code Snippet:
interface Whoa {
public static void doStuff() {
System.out.println("This is not default implementation");
}
}
EDIT:
My IDE is Intellij Idea 13.1. The project SDK is java 7 <1.7.0_25>. The IDE is not showing any compiler error. But, When I compile the code at command line I am getting the following message.
Whoa.java:2: error: modifier static not allowed here public static void doStuff() { ^
From Java 8 you can define static methods in interfaces in addition to default methods.
A static method is a method that is associated with the class in which it is defined rather than with any object. Every instance of the class shares its static methods.
This makes it easier for you to organize helper methods in your libraries; you can keep static methods specific to an interface in the same interface rather than in a separate class.
The following example defines a static method that retrieves a ZoneId
object corresponding to a time zone identifier; it uses the system default time zone if there is no ZoneId
object corresponding to the given identifier. (As a result, you can simplify the method getZonedDateTime
)
Here is code :
public interface TimeClient {
// ...
static public ZoneId getZoneId (String zoneString) {
try {
return ZoneId.of(zoneString);
} catch (DateTimeException e) {
System.err.println("Invalid time zone: " + zoneString +"; using default time zone instead.");
return ZoneId.systemDefault();
}
}
default public ZonedDateTime getZonedDateTime(String zoneString) {
return ZonedDateTime.of(getLocalDateTime(), getZoneId(zoneString));
}
}
For all interesting things in Java 8 read Everything about Java 8