Question

我正在自学AP计算机科学，我对这个问题有点麻烦。

组织通过销售饼干来筹集资金。 cookie订单指定cookie的种类和订购的盒子数量。 CookieOrder类的声明如下所示。

public class CookieOrder
{
/**
Constructs a new
CookieOrder
object.
*/
public CookieOrder(String variety, int numBoxes)
{ /*
implementation not shown
*/ }
/** @return
the variety of cookie being ordered
*/
public String getVariety()
{ /*
implementation not shown
*/ }
/** @return
the number of boxes being ordered
*/
public int getNumBoxes()
{ /*
implementation not shown
*/ }
// There may be instance variables, constr uctors, and methods that are not shown.
}

MasterOrder类维护要购买的cookie列表。 MasterOrder类的声明如下所示。

public class MasterOrder
{
/**
The list of all cookie orders
*/
private List<CookieOrder> orders;
/**
Constructs a new
MasterOrder
object.
*/
public MasterOrder()
{ orders = new ArrayList<CookieOrder>(); }
/**
Adds
theOrder
to the master order.
* @param theOrder
the cookie order to add to the master order
*/
public void addOrder(CookieOrder theOrder)
{ orders.add(theOrder); }
/** @return
the sum of the number of boxes of all of the cookie orders
*/
public int getTotalBoxes()
{ /*
to be implemented in part (a)
*/ }
/**
Removes all cookie orders from the master
order that have the same variety of
*
cookie as
cookieVar
and returns the total number of
boxes that were removed.
* @param cookieVar
the variety of cookies to remove from the master order
* @return
the total number of boxes of
cookieVar
in the cookie orders removed
*/
public int removeVariety(String cookieVar)
{ /*
to be implemented in part (b)
*/ }
//
There may be instance variables, constr
uctors, and methods that are not shown.
}

（a）getTotalBoxes方法计算并返回所有cookie订单的框数之和。如果主订单中没有cookie订单，则该方法返回0.完整方法getTotalBoxes如下。

/** @return
the sum of the number of boxes of all of the cookie orders
*/
public int getTotalBoxes() 

According to college board the answer is:

int sum = 0;

for (CookieOrder a: this.orders)
    sum += a.getNumBoxes();

return sum;

以下是我的问题：

“CookieOrder”是一种类型？
如果我打印出'a'，会打印出什么？
为什么需要关键字“this”？

我更喜欢一个对大脑友好的答案。

Answer 1

1。 “CookieOrder”是一种类型？

这是一种类型，因为它是defined in a class declaration.

2。如果我打印出'a'，会打印出什么？

为什么这是一个假设？运行代码并查看。

3.为什么需要关键字“this”？

在这种情况下不需要。但是，有些人可能会认为它可以改善代码风格/维护/可读性/在这种情况下的任何内容。

Java相关，包括使用构造函数和类

1 个答案: