用类来代替ENUM结构,
具体请看EFFECTIVE JAVA 第21条
简单的例子:
public class Color {
private final String name;
private Color(String name) {this.name = name;}
public String toString() {return name;}
public static final Color RED = new Color("red");
public static final Color YELLOW = new Color("yellow");
public static final Color BLUE = new Color("blue");
}