enumset

问题 I am reading a binary file that has values stored in bit masks, both 1 Byte bit masks and 2 Byte bit masks . Each bit in the masks act as a switch that indicates where an Event has transpired. Example of 1 Byte mask: 00000101 Indicates that Event one and Event 3 has transpired. Example of Enum public enum MyEnum { EventOne, EventTwo, ....; } I have created a Enum MyEnum (as per Item 32 in Effective java, Second Edition) of the events. How can the binary bit masks be read into an EnumSet

问题 I have the following example: import java.util.EnumSet; import java.util.Iterator; public class SizeSet { 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; } In this code I can understand that the Enum creates an Enum type of Sizes. My question is: is largeSize an object of EnumSet type? What

问题 I have an EnumSet and want to convert it to array of its ordinal values. For example: enum MyEnum { A, B, C; } EnumSet enumSet = EnumSet.of(MyEnum.A, MyEnum.C); and what I want to get: [0, 2] 回答1: You should not use the raw type EnumSet without the <MyEnum> part EnumSet<MyEnum> enumSet = EnumSet.of(MyEnum.A, MyEnum.C); A Java 8 solution: MyEnum[] values = MyEnum.values(); int[] ordinals = IntStream.range(0, values.length).filter(i -> enumSet.contains(values[i])).toArray(); A pre-Java 8

问题 I need an EnumSet from an array (which is given through a varargs method parameter). First, I was surprised that there is no varargs constructor method in EnumSet (there is EnumSet#of(E first, E... rest) ). As a workaround, I used the following variant: EnumSet<Options> temp = EnumSet.copyOf(Arrays.asList(options)); However, this triggers a java.lang.IllegalArgumentException: Collection is empty . So, now I ended up with the following, which looks somewhat ridiculous: EnumSet<Options> temp =

问题 While going through the EnumSet<E> of method, I have seen multiple overloaded implementations of of method: public static <E extends Enum<E>> EnumSet<E> of(E e) public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2) . . public static <E extends Enum<E>> EnumSet<E> of(E e1, E e2, E e3, E e4, E e5) and then another overloaded method with varargs public static <E extends Enum<E>> EnumSet<E> of(E first, E... rest) { EnumSet<E> result = noneOf(first.getDeclaringClass()); result.add(first);

问题 I need to create an EnumSet from a Set. I decided to use the EnumSet#copyOf method. However, because of a restriction on this method: the specified collection must contain at least one element (in order to determine the new enum set's element type) I need to ensure that the collection is not empty. The code then becomes: enum Color {RED, GREEN, BLUE}; Set<Color> set = ... // get it from somewhere if (set.isEmpty()) { return EnumSet.noneOf(Color.class); else return EnumSet.copyOf(set); Perhaps

问题 I have an Item object, which has a field that is a Set of ItemTypes: public class Item { EnumSet<ItemType> itemTypeSet; ... public Set<ItemType> getItemTypeSet(){ return this.itemTypeSet; } } ItemType is of course a simple Enum. public Enum ItemType { BOLD, THIN, COOL, ROUND; } In my JSP I would like to use JSTL to see if an item has a specific ItemType, I tried to use the following three snippets but I get no errors and no results. I'm not sure why all 3 are failing. Could somebody explain,

问题 I have an EnumSet and want to convert back-and-forth to/from an array of boolean primitives. If it works better, I could work with a List instead of an array, and/or Boolean objects rather than boolean primitives. enum MyEnum { DOG, CAT, BIRD; } EnumSet enumSet = EnumSet.of( MyEnum.DOG, MyEnum.CAT ); What I want to get on the other end is an array that looks like this: [TRUE, TRUE, FALSE] This Question here is similar to this one, Convert an EnumSet to an array of integers. Differences:

问题 How to store EnumSet in the DB (using Hibernate)? @Entity public class A { public static enum SOME_ENUM { A, B, C }; private EnumSet<SOME_ENUM> myEnumSet = EnumSet.of(SOME_ENUM.A, SOME_ENUM.B); ... ... } If I try to persist the above, I get exception of course. I wanted to use @CollectionOfElements, but it is deprecated. Is there any alternative of @CollectionOfElements? Is there a way to store EnumSet in a single column without writing UserType? Thanks! 回答1: hibernate does not have built in

问题 So i have a bunch of enum's that all extend an interface: public interface MyInterface {} I then have several enums that extend the interface: public enum A implements MyInterface {} public enum B implements MyInterface {} I want a function that will accept only enum's that extend this interface. I cannot do: public void MyFunction(MyInterface input) because, inside the function, I create an EnumSet using EnumSet.of(input). I cannod do public <T extends Enum<T>> void myFunction(T input)