进阶Enum

先说下enum这个类

private enum Color 
	{
		
		red(1), blue(3), green(7);
		static int value;
		 Color(int a)
		{
			value=a;
		}
		 public static int getValue()
		 {
			 return value;
		 }
	}

注意
1、enum就相当于一个类！所以最后没有 分号！！（所以可以在内部，或在外部）

2、枚举值 必须放在类的开头！！

3、如果声明变量 如这里的value也只能在 枚举的值的后面！！

4、可以有diy自己的构造函数！但枚举值必须按照构造函数进行 初始化！！

例如这里 如果写个 black  那他会提示错误1！

下面给出一个nb写的
综合运用

public enum Planet {
    MERCURY (3.303e+23, 2.4397e6),
    VENUS   (4.869e+24, 6.0518e6),
    EARTH   (5.976e+24, 6.37814e6),
    MARS    (6.421e+23, 3.3972e6),
    JUPITER (1.9e+27,   7.1492e7),
    SATURN  (5.688e+26, 6.0268e7),
    URANUS  (8.686e+25, 2.5559e7),
    NEPTUNE (1.024e+26, 2.4746e7);

    private final double mass;   // in kilograms
    private final double radius; // in meters
    Planet(double mass, double radius) 
    {
        this.mass = mass;
        this.radius = radius;
    }
    private double mass()   { return mass; }
    private double radius() { return radius; }

    // universal gravitational constant  (m3 kg-1 s-2)
    public static final double G = 6.67300E-11;

    double surfaceGravity() 
    {
        return G * mass / (radius * radius);
    }
    double surfaceWeight(double otherMass) {
        return otherMass * surfaceGravity();
    }
    public static void main(String[] args) 
    {
       
        double earthWeight = Double.parseDouble("175");
        double mass = earthWeight/EARTH.surfaceGravity();
        for (Planet p : Planet.values())
           System.out.printf("Your weight on %s is %f%n",
                             p, p.surfaceWeight(mass));
    }
}

细心的朋友 注意到没？？？
System.out.printf("Your weight on %s is %f%n",
                             p, p.surfaceWeight(mass));
格式化输出！！
http://lz12366.iteye.com/blog/678613