该代码会产生如下异常: Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Enum at java.util.RegularEnumSet.add(RegularEnumSet.java:18) at java.util.EnumSet.copyOf(EnumSet.java:154) at problems2018_3_23.set.main(set.java:27) 1. 2. 3....
EnumSet.of() 方法被重载以用于一般用途,它的性能往往优于可变参数版本,并且可以添加 EnumSet.of() 方法来灵活地创建具有任意数量实例的枚举。 此外 EnumSet 提供了像 copyOf 方法 (i),noneOf() 通过复制从其他集合的元素,和创建Java中的特定Enum类型的空EnumSet 创建 EnumSet。 如何用Java实现EnumSet EnumSet是一...
在Java中,我们可以通过关键字enum来声明一个枚举类型。枚举类型可以看作是一种特殊的类,它的实例是有限且固定的。以下是一个枚举类型的例子: enum Weekday { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY } 在这个例子中,我们声明了一个枚举类型Weekday,它包含了一周七天的枚举值。 需要注意...
java /** * Bit vector representation of this set. The 2^k bit indicates the * presence of universe[k] in this set. * * 该数的二进制如果比特位为 1,则表示有枚举类型元素 */ private long elements = 0L; 在RegularEnumSet 中使用的是一个 long 整数(二进制)来表示是否添加或者删除了某个枚...
Bit flags, commonly referred to as Bit fields are an efficient way of storing several related boolean values in a single primitive type. Internally represented in binary, you can decide on how large the storage type needs to be - for example, a Java integer will provide you with space for...
*/privatestaticclassSerializationProxy<EextendsEnum<E>>implementsjava.io.Serializable {/** * The element type of this enum set. * *@serial*/privatefinalClass<E> elementType;/** * The elements contained in this enum set. * *@serial*/privatefinalEnum[] elements; ...
They are likely (though not guaranteed) to be much faster than their HashSet counterparts. Even bulk operations execute in constant time if their argument is also an enum set. This class is a member of the Java Collections Framework.
import java.util.EnumMap; import java.util.EnumSet; import java.util.Set;publicclassJavaEnumExamples{publicstaticvoidmain(String[] args) throws IOException{ usingEnumMethods(); usingEnumValueOf(); usingEnumValues(); usingEnumInSwitch(ThreadStatesEnum.START); ...
importjava.util.EnumMap; public class EnumMapExample { public static void main(String[] args) { // Create an EnumMap that contains all constants of the Car enum. EnumMap cars = new EnumMap(Car.class); // Put some values in the EnumMap. ...
你的声明结构太聪明了，真可惜它不起作用。但是EnumSet显然需要先完全初始化枚举。它试图从枚举中获取常量...