Question

I have an assignment that I m not quite sure where to start. This is what I m supposed to do.

Create an abstract class DiscountPolicy. It will have a single abstract method computeDiscount that will return the discount for the purchase of a given number of a single item. The method has two parameters, count (int) and itemCost (float)
Derive a class BulkDiscount from Discount Policy. It will have a constructor that has two parameters, minimum and percent. It will define a method computeDiscount so that if the quantity purchased of an item is more than the minimum, the discount is the percent for the class. ComputeDiscount will return the total discount.
Derive a class BuyNItemsGetOneFree from DiscountPolicy. The class will have a constructor that has a single parameter n. In addition, the class will define the method computeDiscount so that every nth item is free. For example:
If n is 3 and the item cost is $10. There is no discount for the first 2 items. There is a $10 discount for items 3 – 5, there is a $20 discount for the 6th item, etc.
For BuyNItemsGetOneFree – the computeDiscount method will receive the total items bought and the cost for an item, and will return the total discount if applicable.
In your main program, show that the computeDiscount method works for the BulkDiscount and BuyNItemsGetOneFree classes.

这就是我开始建立这一机制的方式。我想把我的方法和参数放在正确的地点,我很想知道,在什么地方我确定我的老师希望我通过的标准。

public class Ex1012 {
    public static void main(String[] args) {
    // TODO Auto-generated method stub

        DiscountPolicy bulk = new BulkDiscount();

        System.out.println();

        DiscountPolicy bngo = new BuyNItemsGetOneFree();        
    }
}

public abstract class DiscountPolicy {  
    abstract void computeDiscount(int count, float itemCost){

        return discount;
    }
}


public class BuyNItemsGetOneFree extends DiscountPolicy {

    BuyNItemsGetOneFree() { 
    }

    BuyNItemsGetOneFree(int n){
        DiscountPolicy.computeDiscount(int count, float itemCost);
        //set n to a variable here??
        //calculations go here
        //Where to set count and itemCost??
    }   
}

public class BulkDiscount extends DiscountPolicy {

    public BulkDiscount(int minimum, float percent){
        if (quantity > minimum){
            super.ComputeDiscount(int count, float itemCost);
        //calculations go here
            //Where to define count, itemCost, minimum, and percent??
        }       
    }   
}

我只是担心这些班级与参数本身之间的关系,因为一旦我有诸如这些班子的多个班子,我就会感到困惑。任何见解都会受到高度赞赏。感谢!

Answer 1

摘要方法可能没有机构,因此,您对<代码>的界定应当:

abstract void computeDiscount(int count, float itemCost);

在扩大抽象类别的具体类别中,你必须采用这种方法。一般来说,抽象的方法与在接口中确定的方法类似(这些方法被宣布,但没有违约执行),但仍然存在差异(可以保护,也可以是私人的一揽子办法,只能由子类实施)。

在大多数情况下,你有一个抽象的班子,提供一些缺省逻辑,并且只是要求分门填写一些取决于具体执行的“空缺”。

基本上,你将参数储存到<代码>。缩略语你们再说一遍,这很可能是错误的。我猜测,你的主人应当把这种方法指直接制造的物体,例如:

DiscountPolicy bngo = new BuyNItemsGetOneFree(5); 
double discountForFour = bngo.computDiscount(4,4.95f);
double discountForFive = bngo.computDiscount(5,4.95f);

请注意,根据您的任务,computeDiscount(...) 方法应退还价值:

......单一抽象的方法 return a. 购买某一项物品的折扣......

Edit:

如何确定计数和项目?

正如我前面说过的那样,你不给他们“set”,而是只用他们计算。

Answer 2

你们需要审查如何界定抽象方法。抽象的方法没有“{}”。应在次类中加以界定。当基类使用抽象方法时,子类通常计算折扣。

Answer 3

首先,抽象的方法没有机构。

第二,它应当计算出的折扣,因此它应当回来,以资补偿。在您的案例中,打折扣就是无效的。

政策

public abstract class DiscountPolicy {  
  abstract float computeDiscount(int count, float itemCost);
}

此外,你不能使用

DiscountPolicy.computeDiscount(int count, float itemCost);

页: 1 贴现方法不是固定方法,甚至不具体。

仅凭一句话,java就是一种敏感的语言,因此,你应当像你所宣称的那样,使用 st子。说明和赔偿差异是两个不同的问题。

Answer 4

<代码>DiscountPolicy是一个基础抽象的类别。就你而言,这为一种代表某种类型差异的类别提供了结构:所有这类类别都应有计算差异的方法,这种方法将根据各自政策计算折扣。这是代表会计的所有阶层必须遵循的合同。

本身并不给出计算折扣的任何逻辑(不采用“违约政策”)。每个阶层都必须提供自己的逻辑。请通过制定<条码>对应代码方法<条码>予以执行。

java的抽象方法没有任何机构。这只是签字:只是合同(结构)和没有执行。

So the computeDiscount in your DiscountPolicy class should look like (Note the ; at the end of the signature itself. Also no {}) :

abstract float computeDiscount(int count, float itemCost);

此外,这一方法将退还购买某一项物品的折扣,因此,返还类型应为<条码>float ,而不是<条码>。

<代码>BuyNItemsGet OneFree和BulkDiscount的班次,为<代码>DiscountPolicy 执行<编码> 比较简明分辨率/代码>。两种次类的“彩虹/代码”方法的逻辑将有所不同,其依据是批量折扣的贴现计算逻辑和购买N免费(在你的工作中给出这一逻辑)。

class BulkDiscount extends DiscountPolicy { //Same signature as computeDiscount of DiscountPolicy //Not abstract, no semicolon at end of signature, has body. //Also called "Concrete" method float computeDiscount(int count, float itemCost) { //The logic as given in the exercise. //Return the discount calculated by the logic } }

请将其作为(Ex1012 s,main方法>)加以测试:

DiscountPolicy bulk = new BulkDiscount(); float discount = bulk.computeDiscount(10, 1); //Data used to test DiscountPolicy bngo = new BuyNItemsGetOneFree(); float discount = bngo.computeDiscount()

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