public static void main(String[] args) {
		
		//角色开始使用的是枪，攻击
		Knight role=new Knight(new Gun());
		role.performAttack();
		
		//现在要换成刀剑，攻击
		role.setWeapon(new Sword());
		role.performAttack();
		
		//现在要换成刀斧头，攻击
		role.setWeapon(new Axe());
		role.performAttack();
	}