How to use EnumSet function in Java for enumeration operations

EnumSet is a practical class in Java, which is used to implement collection operations of enumeration types. EnumSet can be used to perform bit operations, set operations, and other operations on all values ​​of an enumeration type. In the actual development process, using EnumSet can easily operate on multiple enumeration values, improving the readability and maintainability of the code. This article will introduce how to use the EnumSet function in Java to perform enumeration operations.

1. What is EnumSet

EnumSet is an abstract class in Java. It implements the Set interface and can only be used for enumeration type values. The EnumSet class provides some static factory methods that can generate EnumSet instance objects in different ways, for example:

EnumSet<Weekdays> allDays = EnumSet.allOf(Weekdays.class);

EnumSet<Weekdays> weekday = EnumSet.range(Weekdays.MONDAY, Weekdays.FRIDAY);

EnumSet<Weekdays> weekend = EnumSet.complementOf(weekday);

where Weekdays is an enumeration type, which contains the enumeration values ​​of seven days a week, through allOf( ) method can generate an EnumSet instance object containing all enumeration values; the range() method can generate an EnumSet instance object containing an enumeration value within a certain range; the complementOf() method can generate an EnumSet instance object containing all enumeration values ​​except the specified one. The EnumSet instance object that raises the value.

2. Use EnumSet for enumeration operations

1. Basic operations

The basic operations supported by the EnumSet class include add(), remove(), and contains (), size(), etc. These operations are consistent with the Set interface and will not be introduced one by one here.

EnumSet<Weekdays> days = EnumSet.of(Weekdays.MONDAY);
days.add(Weekdays.TUESDAY);
days.remove(Weekdays.MONDAY);

if (days.contains(Weekdays.WEDNESDAY)) {
    System.out.println("Today is Wednesday!");
}
System.out.println(days.size());

2. Set operations

The set operations supported by the EnumSet class include union(), intersection(), complement() and other operations. These operations can conveniently perform bit operations and set operations on two or more EnumSet instance objects.

EnumSet<Weekdays> weekday1 = EnumSet.range(Weekdays.MONDAY, Weekdays.WEDNESDAY);
EnumSet<Weekdays> weekday2 = EnumSet.range(Weekdays.TUESDAY, Weekdays.FRIDAY);
EnumSet<Weekdays> weekend = EnumSet.of(Weekdays.SATURDAY, Weekdays.SUNDAY);

EnumSet<Weekdays> weekdays = EnumSet.of(Weekdays.MONDAY, Weekdays.WEDNESDAY);
// 求并集
EnumSet<Weekdays> union = EnumSet.copyOf(weekdays);
union.addAll(weekday2);
// 求交集
EnumSet<Weekdays> intersection = EnumSet.copyOf(weekdays);
intersection.retainAll(weekday2);
// 求补集
EnumSet<Weekdays> complement = EnumSet.complementOf(weekday1);

// 判断集合包含关系
if (weekdays.containsAll(weekday1)) {
    System.out.println("Weekdays contains Monday to Wednesday!");
}
if (!weekdays.containsAll(weekend)) {
    System.out.println("Weekdays do not contain weekend!");
}

The above code demonstrates how to use EnumSet for set operations. Among them, the copyOf() method can generate an EnumSet instance object containing the specified enumeration value; the addAll() method can add the specified enumeration value to the EnumSet instance object; the retainAll() method can retain the same enumeration as the specified EnumSet instance object. Enumeration value; complementOf() method can generate an EnumSet instance object containing all enumeration values ​​except the specified enumeration value.

3. Conclusion

This article introduces how to use the EnumSet function in Java to perform enumeration operations, mainly including the basic operations and collection operations of EnumSet. By using EnumSet, you can simplify the operation of enumeration types and improve the readability and maintainability of the code. For situations where multiple enumeration values ​​need to be operated on, the flexibility of EnumSet makes the code more concise and easier to maintain.

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