用枚举enum替代int常量

枚举的好处：

1. 类型安全性

2.使用方便性

public class EnumDemo {
    enum Color{
        RED(3),BLUE(5),BLACK(8),YELLOW(13),GREEN(28);
        private int colorValue;
        private Color(int rv){
         this.colorValue=rv;
        }
        private int getColorValue(){
            return colorValue;
        }   

        private int value(){
            return ordinal()+1;
        }
}
    public static void main(String[] args) {
        for(Color s : Color.values()) {
            //enum的values()返回一个数组，这里就是Seasons[]
            System.out.println(s.value()+":"+s.name()+"="+s.getColorValue());
        }
    }
}   

output：

1:RED=3
2:BLUE=5
3:BLACK=8
4:YELLOW=13
5:GREEN=28

其中，

    /**
     * Returns the ordinal of this enumeration constant (its position
     * in its enum declaration, where the initial constant is assigned
     * an ordinal of zero).
     *
     * Most programmers will have no use for this method.  It is
     * designed for use by sophisticated enum-based data structures, such
     * as {@link java.util.EnumSet} and {@link java.util.EnumMap}.
     *
     * @return the ordinal of this enumeration constant
     */
    public final int ordinal() {
        return ordinal;
    }