public enum EnumSeason {
        SPRING, SUMMER, FALL, WINTER;
}

public class EnumTest {
        
        public static void main(String[] args) {
                //枚举类默认有一个values()方法，返回该枚举类的所有实例
                for(EnumSeason s : EnumSeason.values()) {
                        System.out.println(s);
                }
                
                //使用枚举实例时，可通过EnumClass.variable形式来访问
                new EnumTest().judge(EnumSeason.SPRING);
        }
        public  void judge(EnumSeason s) {
                //switch语句里的表达式可以是枚举值
                switch (s) {
                case SPRING:
                        System.out.println("春暖花开，正好踏青");
                        break;
                case SUMMER:
                        System.out.println("夏日炎炎，适合游泳");
                        break;
                case FALL:
                        System.out.println("秋高气爽，进补及时");
                        break;
                case WINTER:
                        System.out.println("冬日雪飘，围炉赏雪");
                        break;
                        
                }
        }
}

public enum Gender {
        MALE, FEMALE;
        public String name;
}

public class GenderTest {
        public static void main(String[] args) {
                // 通过Enum的valueOf()方法来获取指定枚举类的枚举值
                Gender g = Enum.valueOf(Gender.class, "FEMALE");
                g.name = "女";
                
                System.out.println(g + "代表" + g.name);
        }
}

public enum Gender {
        MALE, FEMALE;
        private String name;
        
        public void setName(String name) {
                switch (this) {
                        case MALE:
                                if (name.equals("男")) {
                                        this.name = name;
                                } else {
                                        System.out.println("参数错误");
                                        return;
                                }
                        case FEMALE:
                                if (name.equals("女")) {
                                        this.name = name;
                                } else {
                                        System.out.println("参数错误");
                                        return;
                                }
                                break;
                }
        }
        
        public String getName() {
                return this.name;
        }
}

public class GenderTest {
        public static void main(String[] args) {
                // 通过Enum的valueOf()方法来获取指定枚举类的枚举值
                Gender g = Enum.valueOf(Gender.class, "FEMALE");
                g.setName("女");
                System.out.println(g + "代表" + g.getName());
                
                g.setName("男");
                System.out.println(g + "代表" + g.getName());
        }
}

FEMALE代表女
参数错误
FEMALE代表女

public enum Gender {
        MALE("男"), FEMALE("女");
        private final String name;
        
        private Gender(String name) {
                this.name = name;
        }
        
        public String getName() {
                return this.name;
        }
}

public enum GenderImpl implements GenderDesc{
        MALE("男"), FEMALE("女");
        private final String name;
        
        private GenderImpl(String name) {
                this.name = name;
        }
        
        public String getName() {
                return this.name;
        }

        @Override
        public void info() {
                System.out.println("这是个定义性别的枚举类！");
        }
}

public enum GenderImpl implements GenderDesc{
        MALE("男") {        //花括号部分实际上是一个类体部分
                public void info() {
                        System.out.println("这个枚举值代表男性");
                }
        },
                
        FEMALE("女") {
                public void info() {
                        System.out.println("这个枚举值代表女性");
                }
        };
        
        private final String name;
        
        private GenderImpl(String name) {
                this.name = name;
        }
        
        public String getName() {
                return this.name;
        }

        @Override
        public void info() {
                System.out.println("这是个定义性别的枚举类！");
        }
}

public enum Operation {
        PLUS {
                public double eval(double x, double y) {
                        return x + y;
                }
        },
        
        MINUS {
                public double eval(double x, double y) {
                        return x - y;
                }
        },
        
        TIMES {
                public double eval(double x, double y) {
                        return x * y;
                }
        },
        
        DIVIDE {
                public double eval(double x, double y) {
                        return x / y;
                }
        };
        
        public abstract double eval(double x, double y);
        
        public static void main(String[] args) {
                System.out.println(Operation.PLUS.eval(3, 4));
                System.out.println(Operation.MINUS.eval(5, 4));
                System.out.println(Operation.TIMES.eval(5, 4));
                System.out.println(Operation.DIVIDE.eval(5, 4));
        }
}

7.0
1.0
20.0
1.25