public class Constant { 
  /* 
   * 以下几个变量表示英雄的状态 
   */ 
  public final static int STATUS_WALKING = 0;//走  
  public final static int STATUS_RUNNINGING = 1;//跑 
  public final static int STATUS_ATTACKING = 2;//攻击  
  public final static int STATUS_DEFENDING = 3;//防御  
  public final static int STATUS_DEAD = 4;//挂了  
   
  /* 
   * 以下几个变量表示英雄的等级 
   */ 
  //此处略去N行代码 
} 

hero.setStatus(Contant.STATUS_ATTACKING);

hero.setStatus(666);

public class PlanetWithoutEnum { 
  public static final int PLANET_MERCURY = 0; 
  public static final int PLANET_VENUS = 1; 
  public static final int PLANET_EARTH = 2; 
  public static final int PLANET_MARS = 3; 
  public static final int PLANET_JUPITER = 4; 
  public static final int PLANET_SATURN = 5; 
  public static final int PLANET_URANUS = 6; 
  public static final int PLANET_NEPTUNE = 7; 
} 

public enum Planet { 
  MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, URANUS, NEPTUNE; 
} 

public enum Planet { 
  MERCURY(3.302e+23, 2.439e6),  
  VENUS(4.869e+24, 6.052e6),  
  EARTH(5.975e+24,6.378e6),  
  MARS(6.419e+23, 3.393e6),  
  JUPITER(1.899e+27, 7.149e7),  
  SATURN(5.685e+26, 6.027e7),  
  URANUS(8.683e+25, 2.556e7),  
  NEPTUNE(1.024e+26,2.477e7); 
  private final double mass; // In kilograms 
  private final double radius; // In meters 
  private final double surfaceGravity; // In m / s^2 
 
  // Universal gravitational constant in m^3 / kg s^2 
  private static final double G = 6.67300E-11; 
 
  // Constructor 
  Planet(double mass, double radius) { 
    this.mass = mass; 
    this.radius = radius; 
    surfaceGravity = G * mass / (radius * radius); 
  } 
 
  public double mass() { 
    return mass; 
  } 
 
  public double radius() { 
    return radius; 
  } 
 
  public double surfaceGravity() { 
    return surfaceGravity; 
  } 
 
  public double surfaceWeight(double mass) { 
    return mass * surfaceGravity; // F = ma 
  } 
} 

//注：这里对书中的代码做了微调 
public class WeightTable { 
  public static void main(String[] args) { 
    printfWeightOnAllPlanets(8d); 
  } 
 
  public static void printfWeightOnAllPlanets(double earthWeight) { 
    double mass = earthWeight / Planet.EARTH.surfaceGravity(); 
    for (Planet p : Planet.values()) 
      System.out.printf("Weight on %s is %f%n", p, p.surfaceWeight(mass)); 
  } 
} 

Weight on MERCURY is 3.023254
Weight on VENUS is 7.240408
Weight on EARTH is 8.000000
Weight on MARS is 3.036832
Weight on JUPITER is 20.237436
Weight on SATURN is 8.524113
Weight on URANUS is 7.238844
Weight on NEPTUNE is 9.090108

public enum OperationUseSwitch { 
  PLUS, MINUS, TIMES, DIVIDE; 
 
  double apply(double x, double y) { 
    switch (this) { 
      case PLUS: 
        return x + y; 
      case MINUS: 
        return x + y; 
      case TIMES: 
        return x + y; 
      case DIVIDE: 
        return x + y; 
    } 
    // 如果this不属于上面四种操作符，抛出异常 
    throw new AssertionError("Unknown operation: " + this); 
  } 
} 

public enum Operation { 
  PLUS { 
    double apply(double x, double y) { 
      return x + y; 
    } 
  }, 
  MINUS { 
    double apply(double x, double y) { 
      return x - y; 
    } 
  }, 
  TIMES { 
    double apply(double x, double y) { 
      return x * y; 
    } 
  }, 
  DIVIDE { 
    double apply(double x, double y) { 
      return x / y; 
    } 
  }; 
 
  abstract double apply(double x, double y); 
} 

public enum DayUseAbstractMethod { 
  MONDAY { 
    @Override 
    void apply() { 
      dealWithWeekDays();//伪代码 
    } 
  }, 
  TUESDAY { 
    @Override 
    void apply() { 
      dealWithWeekDays();//伪代码 
    } 
  }, 
  WEDNESDAY { 
    @Override 
    void apply() { 
      dealWithWeekDays();//伪代码 
    } 
  }, 
  THURSDAY { 
    @Override 
    void apply() { 
      dealWithWeekDays();//伪代码 
    } 
  }, 
  FRIDAY { 
    @Override 
    void apply() { 
      dealWithWeekDays();//伪代码 
    } 
  }, 
  SATURDAY { 
    @Override 
    void apply() { 
      dealWithWeekEnds();//伪代码 
    } 
  }, 
  SUNDAY { 
    @Override 
    void apply() { 
      dealWithWeekEnds();//伪代码 
    } 
  }; 
 
  abstract void apply(); 
} 

public enum Day { 
  MONDAY(DayType.WEEKDAY), TUESDAY(DayType.WEEKDAY), WEDNESDAY( 
      DayType.WEEKDAY), THURSDAY(DayType.WEEKDAY), FRIDAY(DayType.WEEKDAY), SATURDAY( 
      DayType.WEEKDAY), SUNDAY(DayType.WEEKDAY); 
  private final DayType dayType; 
 
  Day(DayType daytype) { 
    this.dayType = daytype; 
  } 
 
  void apply() { 
    dayType.apply(); 
  } 
 
  private enum DayType { 
    WEEKDAY { 
      @Override 
      void apply() { 
        System.out.println("hi, weekday"); 
      } 
    }, 
    WEEKEND { 
      @Override 
      void apply() { 
        System.out.println("hi, weekend"); 
      } 
    }; 
    abstract void apply(); 
  } 
} 

public class Text { 
  public enum Style { 
    BOLD, ITALIC, UNDERLINE, STRIKETHROUGH 
  } 
 
  // Any Set could be passed in, but EnumSet is clearly best 
  public void applyStyles(Set<Style> styles) { 
    // Body goes here 
    for(Style style : styles){ 
      System.out.println(style); 
    } 
  } 
 
  // Sample use 
  public static void main(String[] args) { 
    Text text = new Text(); 
    text.applyStyles(EnumSet.of(Style.BOLD, Style.ITALIC)); 
  } 
} 

public class Herb { 
  public enum Type { ANNUAL, PERENNIAL, BIENNIAL } 
 
  private final String name; 
  private final Type type; 
   
  Herb(String name, Type type) { 
    this.name = name; 
    this.type = type; 
  } 
 
  @Override public String toString() { 
    return name; 
  } 
} 

public static void main(String[] args) { 
  Herb[] garden = { new Herb("Basil", Type.ANNUAL), 
      new Herb("Carroway", Type.BIENNIAL), 
      new Herb("Dill", Type.ANNUAL), 
      new Herb("Lavendar", Type.PERENNIAL), 
      new Herb("Parsley", Type.BIENNIAL), 
      new Herb("Rosemary", Type.PERENNIAL) }; 
 
  // Using an EnumMap to associate data with an enum - Page 162 
  Map<Herb.Type, Set<Herb>> herbsByType = new EnumMap<Herb.Type, Set<Herb>>( 
      Herb.Type.class); 
  for (Herb.Type t : Herb.Type.values()) 
    herbsByType.put(t, new HashSet<Herb>()); 
  for (Herb h : garden) 
    herbsByType.get(h.type).add(h); 
  System.out.println(herbsByType); 
 
}