枚举使用enum定义，默认继承java.lang.Enum，不再继承Object
枚举中必须在第一行列出所有实例，枚举的构造器未接收形参的情况下，实例可以不写括号()
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public enum Direction{
North, South, East, West;
Direction() {
}
}
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当然，如果你想写括号也可以写
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| public enum Direction{
North(), South(), East(), West();
Direction() {
}
}
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不过当构造器接收了参数的时候，则一定要在第一行列出的实例中传入对应参数
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public enum Direction{
North(""), South(""), East(""), West("");
Direction(String s) {
}
}
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实际上，上述枚举类等同于如下
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| public class Direction{
public static final Direction North = new Direction("");
public static final Direction South = new Direction("");
public static final Direction East = new Direction("");
public static final Direction West = new Direction("");
private Direction(String s) {
}
}
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在使用上，也大同小异
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| public static void main(String[] args) {
check(Direction.North);
check(Direction.South);
}
private static void check(Direction direction) {
if (direction == Direction.North) {
System.out.println("North");
} else if (direction == Direction.South) {
System.out.println("South");
}
}
public enum Direction{
North, South, East, West;
}
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用switch更为便捷
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| public static void main(String[] args) {
check(Direction.North);
check(Direction.South);
}
private static void check(Direction direction) {
switch (direction) {
case North:
System.out.println("North");
break;
case South:
System.out.println("South");
break;
}
}
public enum Direction{
North, South, East, West;
}
|