How to use Java Enum class?

Java enum classes can be used by following these steps:

1. a set of values that a variable can take

public enum DayOfWeek {
  MONDAY,
  TUESDAY,
  WEDNESDAY,
  THURSDAY,
  FRIDAY,
  SATURDAY,
  SUNDAY
}

1. Using enumerated constants: it is possible to access them by their enumerated constant name. For example:

DayOfWeek day = DayOfWeek.MONDAY;
System.out.println(day);  // 输出: MONDAY

1. By using enum classes, you can include methods that can be called through enum constants. For example:

public enum DayOfWeek {
  // ...

  public boolean isWeekend() {
    return this == SATURDAY || this == SUNDAY;
  }
}

DayOfWeek day = DayOfWeek.SATURDAY;
System.out.println(day.isWeekend());  // 输出: true

1. Using static methods and properties in an enumeration: Enumerations can contain static methods and properties, which can be directly called using the enumeration name. For example:

public enum DayOfWeek {
  // ...

  public static DayOfWeek fromString(String dayStr) {
    for (DayOfWeek day : DayOfWeek.values()) {
      if (day.name().equalsIgnoreCase(dayStr)) {
        return day;
      }
    }
    throw new IllegalArgumentException("Invalid day of week: " + dayStr);
  }
}

DayOfWeek day = DayOfWeek.fromString("monday");
System.out.println(day);  // 输出: MONDAY

These are the basic steps for using Java enumeration classes, which can be expanded and customized as needed.