JAVA对象数组程序输出错误(初级)

Question

我的作业是计算一年中产生的二氧化碳量一个家庭，并比较回收如何减少其二氧化碳足迹。程序中有两个类:CO2FromWaste 和 CO2FromWasteTester。

第一类，CO2FromWaste 是:

public class CO2FromWaste
{
    //declaration of private instance variables
    private int numPeople;
    private boolean Paper, Plastic, Glass, Cans;
    private double grossWasteEmission, wasteReduction, netWasteReduction;

    //constructor 
    CO2FromWaste(int people, boolean paper, boolean plastic, boolean glass, boolean cans){
        numPeople = people;
        Paper = paper;
        Plastic = plastic;
        Glass = glass;
        Cans = cans;
        grossWasteEmission = 0.0;
        wasteReduction = 0.0;
        netWasteReduction = 0.0;
    }
    public void calcGrossWasteEmission(){
        grossWasteEmission = numPeople * 1018;

    }
    public double getGrossWasteEmission(){
        return grossWasteEmission;
    }
    public void calcWasteReduction(){
        if (Paper == true){
            wasteReduction = numPeople * 184;
        }
        if (Plastic == true){
            wasteReduction += (numPeople * 25.6);
        }
        if (Glass == true){
            wasteReduction+= (numPeople*46.6);
        }
        if (Cans == true){
            wasteReduction+=(numPeople*165.8);
        }

    }
    public double getWasteReduction()
    {
        return wasteReduction;
    }
    public void calcNetWasteReduction(){
        netWasteReduction = grossWasteEmission = wasteReduction;

    }
    public double getNetWasteReduction(){
        return netWasteReduction;
    }
    public int getNumPeople(){
        return numPeople;
    }
    public boolean getPaper(){
        return Paper;
    }
    public boolean getPlastic(){
        return Plastic;
    }
    public boolean getGlass(){
        return Glass;
    }
    public boolean getCans(){
        return Cans;
    }
}

第二类，CO2FromWasteTester 是:

import java.util.ArrayList;
public class CO2FromWasteTester
{
    public static void main(String[]args){
        ArrayList<CO2FromWaste> waste = new ArrayList<CO2FromWaste>();

        waste.add(new CO2FromWaste(1, true, true, true, true));
        waste.add(new CO2FromWaste(3, true, false, true, true));
        waste.add(new CO2FromWaste(4, false, false, false, false));
        waste.add(new CO2FromWaste(1, true, true, true, true));
        waste.add(new CO2FromWaste(1, true, true, true, true));

        CO2FromWaste wasteRecord;
        for (int index = 0; index < waste.size(); index++){
            wasteRecord = waste.get(index);
            wasteRecord.calcGrossWasteEmission();
            wasteRecord.calcWasteReduction();
            wasteRecord.calcNetWasteReduction();
        }
        System.out.println("                   Household Waste Recycled                    Total    Pounds of CO2    Net");
        System.out.println(" Index    People    Paper     Plastic     Glass     Cans     Emission     Reduction    Emission ");

        for (int index = 0; index < waste.size(); index ++)
        {
            wasteRecord = waste.get(index);
            System.out.printf("%3d %9d %10s %10s %10s %10s %12.2f %10.2f %10.2f%n",index,wasteRecord.getNumPeople(),wasteRecord.getPaper(), wasteRecord.getPlastic(), wasteRecord.getGlass(),wasteRecord.getCans(),wasteRecord.getGrossWasteEmission(),wasteRecord.getWasteReduction(),wasteRecord.getNetWasteReduction());
        }
    }
}

输出应该像表格一样读起来，标题下有正确的数据。对于第一行，输出应该是

0   1   true   true   true   true   1018.00   422.00   596.00 

但是上面写着

0  1   true   true   true   true    422.00   422.00   422.00

总排放部分的开头有问题，该部分应该相当简单，因为它所需要做的就是将给定的人数乘以 1018。我不知道从这里该怎么做，希望得到一些帮助。

Answer 1

这就是问题:

public void calcNetWasteReduction(){
    netWasteReduction = grossWasteEmission = wasteReduction;    
}

这相当于:

public void calcNetWasteReduction(){
    grossWasteEmission = wasteReduction;    
    netWasteReduction = grossWasteEmission;
}

换句话说，它在不应该修改的时候修改了grossWasteEmission。我怀疑你想要:

public void calcNetWasteReduction(){
    netWasteReduction = grossWasteEmission - wasteReduction;    
}

换句话说，将第二个 = 改为 -。

老实说，根本不清楚为什么你有这三个单独的方法 - 为什么不在构造函数中执行计算？或者在 getter 方法中(完全删除中间字段)？

此外，考虑对减少浪费的类型(PAPER、GLASS、PLASTIC)进行枚举，并采用其中的 EnumSet。如果您确实将它们保留为单独的参数，我强烈建议您将名称更改为更常规的 Java(paper 而不是 Paper 等)，并使用 if (paper) 而不是 if (paper == true) 等。一般来说，避免对 boolean 常量进行显式检查。