java - 错误代码不兼容的类型 : possible lossy conversion from double to int

Question

我正在根据教科书的示例更改此代码，以与双数组兼容。代码中有几个地方我不确定如何修复错误“不兼容的类型:从 double 到 int 可能有损转换”

temp = numberList[max];    
numberList[max] = numberList[numberList.length - i - 1];
numberList[numberList.length - i - 1] = temp;

if (numberList[i] > numberList[index] )

j = i;
temp = numberList[i];

这些显示错误“不兼容的类型:从 double 到 int 可能有损转换。”

我在第一次使用indexOfLargestElement时也收到错误，“找不到符号。”

package week5;
import java.util.Arrays;
/**
 *
 * @author meowens
 */
public class Week5 {

/**
 * @param args the command line arguments
 */

public static void selectionSort( double [] numberList) {

    double temp; 
    double max;

    for (double i = 0; i < numberList.length - 1; i++)  
    {
        max = indexOfLargestElement( numberList, numberList.length - i);

        temp = numberList[max];
        numberList[max] = numberList[numberList.length - i - 1];
        numberList[numberList.length - i - 1] = temp;
    }
}
private static double indexOfLarggestElement( double [] numberList, double size )
{
    double index = 0;
    for ( double i = 1; i < size; i++)
    {
        if (numberList[i] > numberList[index] )
            index = i;
    }
    return index;
}
public static void insertionSort ( double [] numberList)
{
    int j, temp;

    for ( double i = 1; i < numberList.length; i++ )
    {
        j = i;
        temp = numberList[i];

        while ( j != 0 && numberList[j - 1] > temp )
        {
            numberList[j] = numberList[j - 1];
            j--;
        }

        numberList[j] = temp;
    }
    // TODO code application logic here



    // assigning values
    numberList[0] = 53.5;
    numberList[1] = 60.3;
    numberList[2] = 96.2;
    numberList[3] = 53.3;
    numberList[4] = 56.4;
    numberList[5] = 52.7;
    numberList[6] = 76.4;
    numberList[7] = 77.5;
    numberList[8] = 71.0;
    numberList[9] = 78.2;

    numberList[10] = 65.2;
    numberList[11] = 59.3;
    numberList[12] = 80.5;
    numberList[13] = 92.1;
    numberList[14] = 85.7;
    numberList[15] = 78.7;
    numberList[16] = 66.2;
    numberList[17] = 88.8;
    numberList[18] = 50.2;
    numberList[19] = 73.4;

    }

}

我确信还有其他简单的错误我还没有发现，因为我还没有机会调试和校对代码，而且我对 Java 和一般编程也很陌生。

感谢您的帮助!

Answer 1

for ( double i = 1; i < numberList.length; i++ )

除了 byte、short、int 之外，您不能使用任何其他类型来通过数组进行索引，因此会出现问题。 char 值也可以用作索引值，因为它们会受到一元数字提升并成为 int 值，但使用 char 值的情况很少见作为索引器。

确保在使用 double 类型变量在数组中进行索引的地方，将 double 类型变量更改为 int 类型变量。

Java 文档

Arrays must be indexed by int values; short, byte, or char values may also be used as index values because they are subjected to unary numeric promotion (§5.6.1) and become int values.

An attempt to access an array component with a long index value results in a compile-time error.