Java中Enum、EnumMap、EnumSet使用示例

1.Enum示例

public enum Day {
SUNDAY(1),
MONDAY(2),
TUESDAY(3),
WEDNESDAY(4),
THURSDAY(5),
FRIDAY(6),
SATURDAY(7)

private int value;

// 私有构造
private Day(int value) {this.value = value; }

// 重写toString方法
@Override
public String toString() {
switch(this) {
case FRIDAY:
return "Friday: " + value;
case MONDAY:
return "Monday: " + value;
case SATURDAY:
return "Saturday: " + value;
case SUNDAY:
return "Sunday: " + value;
case THURSDAY:
return "Thursday: " + value;
case TUESDAY:
return "Tuesday: " + value;
case WEDNESDAY:
return "Wednesday: " + value;
default:
return null;
}
}

}

public enum Car {
AUDI {
@Override
public int getPrice() {
return 25000;
}
},
MERCEDES {
@Override
public int getPrice() {
return 30000;
}
},
BMW {
@Override
public int getPrice() {
return 20000;
}
};

public abstract int getPrice();
}

2.EnumMap示例

import java.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.
cars.put(Car.BMW, Car.BMW.getPrice());
cars.put(Car.AUDI, Car.AUDI.getPrice());
cars.put(Car.MERCEDES, Car.MERCEDES.getPrice());

// Print the values of an EnumMap.
for(Car c: cars.keySet())
System.out.println(c.name());

System.out.println(cars.size());

// Remove a Day object.
cars.remove(Car.BMW);
System.out.println("After removing Car.BMW, size: " + cars.size());

// Insert a Day object.
cars.put(Car.valueOf("BMW"), Car.BMW.getPrice());
System.out.println("Size is now: " + cars.size());
}
}

3.EnumSet示例

import java.util.EnumSet;

public class EnumSetExample {
public static void main(String[] args) {
// Create an EnumSet that contains all days of the week.
EnumSet week = EnumSet.allOf(Day.class);

// Print the values of an EnumSet.
for(Day d: week)
System.out.println(d.name());

System.out.println(week.size());

// Remove a Day object.
week.remove(Day.FRIDAY);
System.out.println("After removing Day.FRIDAY, size: " + week.size());

// Insert a Day object.
week.add(Day.valueOf("FRIDAY"));
System.out.println("Size is now: " + week.size());
}
}