Question

这个程序需要迭代一个数组列表来将所有整数添加到一起，但是我得到一个“int not be dereferenced”错误。我认为int不能用在数组列表中，但这就是它在指南程序中的表现，我不知道该怎么做。第一种方法需要计算总人数然后乘以平均排放量1018.请帮助我。

这段代码已经提供给我了，当他们给你代码时，你不会改变他们给你的东西，你只需添加缺少的东西。

方法类

//  This class instantiates CO2FromWaste(8.11) objects with 8 private instance variables.
//  It contains three mutator methods to calculate the pounds of CO2: in total emissions,
//  emission reductions, and net emissions.  It contains getter methods for each private
//  instance variables.  Private instance variables include myNumPeople, myPaper, myPlastic,
//  myGlass, myCans, myEmissions, myReduction, and myNetEmissions.
// 
public class CO2FromWaste
{
   private int myNumPeople;
   private boolean myPaper, myPlastic, myGlass, myCans;
   private double myEmissions, myReduction, myNetEmissions;

   //
    // Constructor for objects of type CO2FromWaste
    // @param numPeople number of people in a household
    // @param paper whether or not paper is recycled
    // @param plastic whether or not plastic is recycled
   //  @param glass whether or not glass is recycled
    // @param cans whether or not cans are recycled

   CO2FromWaste(int numPeople, boolean paper, boolean plastic, boolean glass, boolean cans)
   {
       myNumPeople = numPeople;
       myPaper = paper;
       myPlastic = plastic;
       myGlass = glass;
       myCans = cans;
       myEmissions = 0.0;
       myReduction = 0.0;
       myNetEmissions = 0.0;
   }

   //
   //  Mutator method to calculate the total emissions, without any recycling (no parameters)

这是第一个问题的来源。

   public void calcGrossWasteEmission()
   {
       double sum = 0;
       for(int i = 0; i< myNumPeople.size(); i++)
       {
       sum += myNumpeople.get(i);
    }
    myEmissions = sum  1018;
   }

   //
    // Mutator method to calculate the emission reduction from recycling (no parameters)

   public void calcWasteReduction()
   {
       if(myPaper)
       {
           myReduction += (184.0  myNumPeople);
       }

      // fill in rest of method here //



   }

   //
   //  Mutator method to calculate the net emissions (no paramters)

   public void calcNetWasteReduction()
   {
        // fill in rest of method here //
   }

   //
   //  Getter method to return the number of people (no paramters)

   public int getNumPeople()
   {
       return myNumPeople;
   }

   //
    // Getter method to return paper's recycled status (true or false) (no paramters)

   public boolean getPaper()
   {
       return myPaper;
   }

   //
    // Getter method to return glass's recycled status (true or false) (no paramters)

   public boolean getGlass()
   {
       return myGlass;
   }

   //
   //  Getter method to return plastic's recycled status (true or false) (no paramters)

   public boolean getPlastic()
   {
       return myPlastic;
   }

   //
   //  Getter method to return cans' recycled status (true or false) (no paramters)

   public boolean getCans()
   {
       return myCans;
   }

   //
   //  Getter method to return the total emissions (no paramters)

   public double getEmissions()
   {
       return myEmissions;
   }

   //
   //  Getter method to return the reduction amount (no paramters)

   public double getReduction()
   {
       return myReduction;
   }

   //
   //  Getter method to return the net emissions (no paramters)

   public double getNetEmissions()
   {
       return myNetEmissions;
   }
}

Tester Class

/**
 * @purpose: Calculate the CO2 from household waste 8.11
 *
 * @author:
 * @version:
 */
import java.util.ArrayList;

public class CO2FromWasteTester
{
   public static void main(String[] args)
   {
       ArrayList<CO2FromWaste> cO2 = new ArrayList<CO2FromWaste>();
           // adding households
           cO2.add(new CO2FromWaste(1,true,true,true,true));
           cO2.add(new CO2FromWaste(3,true,false,true,true));
           cO2.add(new CO2FromWaste(4,false,false,false,false));
           cO2.add(new CO2FromWaste(1,true,true,true,true));
           cO2.add(new CO2FromWaste(1,true,true,true,true));

       for(CO2FromWaste dataRecord : cO2)
       {
           dataRecord.calcGrossWasteEmission();
           dataRecord.calcWasteReduction();
           dataRecord.calcNetWasteReduction();
       }

       System.out.println("|       |        |                                         |             Pounds of CO2             |");
       System.out.println("|       |        |       Household Waste Recycled          |   Total    |             |     Net    |");
       System.out.println("| Index | People |  Paper   |  Plastic |  Glass  |  Cans   |  Emission  |  Reduction  |  Emission  |");
       System.out.println("|-------|--------|----------|----------|---------|---------|------------|-------------|------------|");

       CO2FromWaste dataRecord;

       for(int index = 0; index < cO2.size(); index ++)
       {
           dataRecord = cO2.get(index);
           System.out.printf("|   %1d   |    %2d  |   %-5b  |  %-5b   |  %-5b  |  %-5b  |  %8.2f  |   %7.2f   |   %8.2f |%n", index, dataRecord.getNumPeople(), dataRecord.getPaper(), dataRecord.getPlastic(), dataRecord.getGlass(), dataRecord.getCans(), dataRecord.getEmissions(), dataRecord.getReduction(), dataRecord.getNetEmissions());
       }
   }
}

Answer 1

myNumPeople是int，但您尝试使用它，就好像它是List myNumpeople.get(i)，myNumpeople.size()等。 ..）。

您应该更改myNumPeople的类型。

Answer 2

int和boolean是原始数据类型;他们不是对象，所以他们无法进入List。相反，请使用Integer和Boolean。

编辑：伊兰也是对的。

如何在ArrayList中使用int和booleans

2 个答案: