Question

我再一次把我的大脑作为错误信息不断涌来。我正在学习如何使用数组 - 常规和多维。我遇到问题a）用销售数据填充数组，还有一个部分，我得到“无法将字符串转换为int”。当我修改这个数组以获得一个字符串值时， - 然后我得到一个翻转错误， - “无法将int转换为String。感谢任何帮助。谢谢。

    public class Sales{

       public static void main (String []Args)
       {   

        //a single dimension array containing the following customer names

       String [] Names = {"John Doe","Pete BuysAlot","Joe Stingy","Mary       LikesOurStuff" } ;
       //  for(int 0;i<Names.length; i++)            
          // System.out.printl=n(Names[i]);}
       //a single dimension array containing the names of  //each                   month               
       String[]Months= new String [11];

           Months[0] = "   Jan   ";
           Months[1] = "   Feb   ";
           Months[2] = "   Mar   ";
           Months[3] = "   Apr   ";
           Months[4] = "   May   ";  
           Months[5] ="    June  ";
           Months[6] ="    July  ";
           Months[7] ="    Aug   ";
           Months[8] ="    Sept  ";
           Months[9] ="    Oct   ";
           Months[10]="    Nov   ";
           Months[11]="    Dec   "; 




         // this next section creates the variables and data to create and initialize          
        //  a two dimension array that reflects the purchases each person made per month.
       //It will have the initial data in the following table

     int[][]slsData = { {200,50,30,300,155,220,80,70,95,110,3,400},
                 { 1200,2000,1500,900,1300,800,750,500,900,1200,1500,2000},
                      {10,0,0,20,5,30,10,0,0,10,15,0},
                      {500,100,200,400,600,200,150,155,220,336,43 ,455}
                               };

           String [][] slsTablePP = slsData[3][Months]; //here is where an  error occurance is. [months] is a declared as a new string array but errors.
           {
              for (int row = 0; row <Names.length; row++)
                 for (int col = 0;  col<Months.length; col++)
                 System.out.println(slsTablePP[row][col]);    }   


           // array to hold sales figures totals by  month 
              for( int x=0;x<mthlySales-1;x++)
             System.out.println(Names[i] + mthlySls[x]);
         }
     }
 }

Answer 1

slsData[3][Months]

Months在这里应该是一个整数，以访问slsData中第3个数组的第n个元素。但Months的类型为String[]，因此没有意义。也许你要传递的是Months数组的长度。在这种情况下，您将使用slsData[3][Months.length]。

但是因为slsData是一个int数组的数组，slsData[3][12]就是一个int。因此，您无法将其分配给String[][]类型的变量。

请注意，您应该遵守Java命名约定。变量应该有有意义的名称，由单词组成（slsData和slsTablePP是什么意思？），并且应该以小写字母开头（即months，而不是Months）。

Answer 2

 String [][] slsTablePP = slsData[3][Months];

月份不是整数。您不能直接将一个int数组转换为String数组。要将整数数组转换为字符串数组，请查看Converting an int array to a String array

String[]Months= new String [11];

上述数组的大小应为12。

Answer 3

Months只是String数组的名称。为了访问数组中的各个值，您必须使用数组运算符[]将所需值传递给它。

例如：

String[] stringArray = new String[4];
String fourthString = stringArray[3];

或

String[] stringArray = new String[someList.size()]
for (int i=0; i<stringArray.length; i++) {
   stringArray[i] = someList.get(i);
   //some other stuff maybe
}

Answer 4

显然，这一行是错误的：

String [][] slsTablePP = slsData[3][Months];

数组是类型的，你无法将int[][]神奇地转换为String[][]，而且，在Java中，数组始终由int索引。其中slsData[3][Months] Months类型为String[][]的{{1}}没有任何意义请注意，在某些语言中，如Python，您有关联数组（Map和Java中的派生类），它们可以具有数组语法，其中字符串作为索引，例如

# python syntax
salesByMonth = {}
salesByMonth["jan"] = 2000;
salesByMonth["feb"] = 500;

声明Months数组时还有另一个问题。在

String[] Months= new String [11]; // <= should be 12 !

值[11]是数组的大小，而不是最后一个索引，因此它应该是12。在Java数组中，0已编入索引。

下面我举一个注释示例，说明如何匹配不同的数据数组。

public class Sales{
    public static void main (String []Args) {     
        //a single dimension array containing the following customer names
        String [] Names = {"John Doe","Pete BuysAlot","Joe Stingy","Mary LikesOurStuff" } ;
        //a single dimension array containing the names of each month               
        String[]Months= new String [12]; // <= 12 is the size not the last index !
        Months[0] = "   Jan   "; Months[1] = "   Feb   ";
        Months[2] = "   Mar   "; Months[3] = "   Apr   ";
        Months[4] = "   May   "; Months[5] = "   June  ";
        Months[6] = "   July  "; Months[7] = "   Aug   ";
        Months[8] = "   Sept  "; Months[9] = "   Oct   ";
        Months[10]= "   Nov   "; Months[11]= "   Dec   "; 

         // two dimension array that reflects the purchases each person made per month.
        int[][]slsData = { 
                { 200,   50,   30, 300,  155, 220,  80,  70,  95,  110,   3,   400},
                {1200, 2000, 1500, 900, 1300, 800, 750, 500, 900, 1200, 1500, 2000},
                {  10,    0,    0,  20,    5,  30,  10,   0,   0,   10,   15,    0},
                { 500,  100,  200, 400,  600, 200, 150, 155, 220,  336,  43 ,  455}
        };

        // match the sales data with name & month through the _indexes_ 
        // in the arrays. Here iName [0, 3] and iMonth [0, 11] will
        // give the sales amount for a (name, month): slsData[iName][iMonth]
        for (int iName = 0; iName < Names.length; iName++) {
            System.out.println("\nSales for "+Names[iName]);
            int total = 0; // total (re)set to 0 for each name
            for (int iMonth = 0; iMonth < Months.length; iMonth++) {
                System.out.println(Months[iMonth] + slsData[iName][iMonth]);
                total += slsData[iName][iMonth];
            }
            System.out.println("Total sales for "+Names[iName] + ": "+total);
        }
    }
}

无法将int转换为String，/无法将String转换为int [] []

4 个答案: