EnumSet
In this chapter you will learn:
Use EnumSet
EnumSet extends AbstractSet and implements Set.
It is specifically for use with keys of an enum type.
It is a generic class that has this declaration:
class EnumSet<E extends Enum<E>>
E specifies the elements.
EnumSet defines no constructors.
It uses the factory methods to create objects.
The EnumSet class provides a Set
implementation that is based on a bitset.
Its elements are constants that must come from the same enum.
Null elements are not permitted.
The following code use the EnumSet
import java.util.EnumSet;
import java.util.Iterator;
import java.util.Set;
/*from ja v a 2s. c o m*/
enum Weekday {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}
public class Main {
public static void main(String[] args) {
Set<Weekday> daysOff = EnumSet.of(Weekday.SUNDAY, Weekday.MONDAY);
Iterator<Weekday> iter = daysOff.iterator();
while (iter.hasNext())
System.out.println(iter.next());
}
}
The code above generates the following result.
Create EnumSet with a list of enum value list
import java.util.EnumSet;
import java.util.Iterator;
//from j ava 2 s . c om
public class Main {
public static void main(String[] args) {
EnumSet largeSize = EnumSet.of(Size.XL,Size.XXL,Size.XXXL);
for(Iterator it = largeSize.iterator();it.hasNext();){
Size size = (Size)it.next();
System.out.println(size);
}
}
}
enum Size {
S, M, L, XL, XXL, XXXL;
}
The output:
Next chapter...
What you will learn in the next chapter: