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1、策略枚举

1、策略枚举

• 使用策略枚举消除大量使用的if else

• 使用大量 if-else

public class IfService {public String getToDo(String day) {if ("Monday".equals(day)) {return "今天上英语课";} else if ("Tuesday".equals(day)) {return "今天上语文课";} else if ("Wednesday".equals(day)) {return "今天上数学课";} else if ("Thursday".equals(day)) {return "今天上音乐课";} else if ("sunday".equals(day)) {return "今天上编程课";} else {return null;}}public static void main(String[] args) {IfService ifService = new IfService();System.out.println(ifService.getToDo("Monday"));}
}

结果：

• 使用枚举类进行优化大量if -else

public class CheckDay {public String day(DayEnum dayEnum){return  dayEnum.toDo();}}

public enum DayEnum {Monday{@Overridepublic String toDo(){return "周一";}},Tuesday{@Overridepublic String toDo(){return "周二";}},Wendsday{@Overridepublic String toDo(){return "周三";}},Thursday{@Overridepublic String toDo(){return "周四";}},Friday{@Overridepublic String toDo(){return "周五";}};public abstract String toDo();
}

    public static void main(String[] args) {CheckDay checkDay = new CheckDay();//可以传递参数选择哪个 枚举对象String monday = checkDay.day(DayEnum.valueOf("Monday"));System.out.println(monday);}
}

• 另一种情况

    public String getToDo(String day) {//第一种情况
//        if ("Monday".equals(day)) {
//            return "今天上英语课";
//        } else if ("Tuesday".equals(day)) {
//            return "今天上语文课";
//        } else if ("Wednesday".equals(day)) {
//            return "今天上数学课";
//        } else if ("Thursday".equals(day)) {
//            return "今天上音乐课";
//        } else if ("sunday".equals(day)) {
//            return "今天上编程课";
//        } else {
//            return null;
//        }//第二种情况if("Monday".equals(day)||"Tuesday".equals(day)||"Wednesday".equals(day)){return "今天上英语课";}else if("Thursday".equals(day)){return null;}return null;}

public class CheckDay {public String dayNew(DayEnumNew dayEnumNew) {return dayEnumNew.toDo();}
}

public enum DayEnumNew {Monday(Type.ENGLISH, "星期一"),Tuesday(Type.ENGLISH, "星期二"),Wednesday(Type.ENGLISH, "星期三"),Thursday(Type.CHINESE, "星期四");private final Type type;private final String day;DayEnumNew(Type type, String day) {this.type = type;this.day = day;}String toDo(){return type.toDo();}/*** 内部策略枚举*/private enum Type {ENGLISH {@Overridepublic String toDo() {return "今天上英语课";}},CHINESE {@Overridepublic String toDo() {return "今天上语文课";}};public abstract String toDo();}
}

    public static void main(String[] args) {CheckDay checkDay = new CheckDay();//可以传递参数选择哪个 枚举对象
//        String monday = checkDay.day(DayEnum.valueOf("Monday"));
//        System.out.println(monday);String monday = checkDay.dayNew(DayEnumNew.valueOf("Monday"));String thursday = checkDay.dayNew(DayEnumNew.valueOf("Thursday"));String thursday1 = checkDay.dayNew(DayEnumNew.valueOf("Wednesday"));System.out.println(monday);System.out.println(thursday);System.out.println(thursday1);}

结果：