Java吃豆子游戏-2 接口

开始其他代码类编写之前，把共享的常量写到一个接口里，

interface GameConstants {
	int EAST = 21;
	int WEST = 22;
	int NORTH= 23;
	int SOUTH= 24 ;
	
	int EATER = 1111;
	int ENEMY = 1112;
	
	int MIN_VELOCITY = 0;
	int MAX_VELOCITY = 6;
}