Java之实现枚举原理

public class EnumTest {

public static void main(String[] args) {

WeekDay weekDay = WeekDay.MON;
System.out.println(weekDay.nextDay().toString());
}
}

public class WeekDay {

private WeekDay(){}

public final static WeekDay SUN = new WeekDay();
public final static WeekDay MON = new WeekDay();

public WeekDay nextDay(){

if(this==SUN){
return MON;
}else{
return SUN;
}
}

public String toString(){

return this ==SUN?"SUN":"MON";
}
}

另一种实现
public abstract class WeekDay {

private WeekDay(){}

public final static WeekDay SUN = new WeekDay(){

public WeekDay nextDay(){
return MON;
}
};
public final static WeekDay MON = new WeekDay(){
public WeekDay nextDay(){
return SUN;
}
};

public abstract WeekDay nextDay();

public String toString(){

return this ==SUN?"SUN":"MON";
}
}