java - 为什么会生成“索引越界”错误？

我试图弄清楚为什么createArithmeticSeq中的循环超出范围，但无法解决。当i = listSize-1时，循环应该停止，因为它是（i = 0; i

import java.util.*;

public class MagicSquare
{
static int row, col, n, rows, columns, listSize;
static Scanner console = new Scanner (System.in);

这是发生问题的地方：

public static void createArithmeticSeq(int [] list)
    {
    //prompt user for array size
    System.out.println("Enter size of array (in form nxn), n:");
    n = console.nextInt();
    rows = n;
    columns = n;
    listSize= (n*n);
    int first;
    int diff;
    //prompt user for first and diff
    System.out.println("Enter first and diff : ");
    first = console.nextInt();
    diff  = console.nextInt();
    //process to create list of n*n elements
    for (int i=0; i<listSize; i++)
    {
        list[i]=first+i*diff;
    }
}

这是其余的代码：

public static void matricize (int [] list, int [][] matrix)
{
    int i = 0;
//loop through each row
    for (row=0; row<matrix.length; row++)
    {
    //loop through each column
        for (col=0; col<matrix[row].length; col++)
        {
        //populate matrix with values from list
        matrix[row][col] = list[i++];
        }
     }
}
public static void printMatrix(int [][] matrix)
{

    for (row=0; row < matrix.length; row++)
    {
        for (col=0; col < matrix[row].length; col++)
            System.out.printf("%2d" + " ", matrix[row][col]);

        System.out.println("\n");
    }
}

public static void reverseDiagonal(int [] [] matrix)
{
    int temp;
    for (row=0; row<matrix.length / 2; row++)
    {
        temp = matrix[row][row];
        matrix[row][row] =
            matrix[matrix.length - 1 - row] [matrix.length - 1 - row];
        matrix[matrix.length - 1 - row][matrix.length - 1 - row] = temp;
    }
    for (row=0; row<matrix.length / 2; row++)
    {
        temp = matrix[row][matrix.length - 1 - row];
        matrix[row][matrix.length - 1 - row] =
            matrix[matrix.length - 1 - row][row];
        matrix[matrix.length - 1 - row][row] = temp;
    }
}

public static void magicCheck(int [] list, int [] [] matrix)
{
    int sum=0, sumRow=0, sumCol=0, sumDiag1=0, sumDiag2=0, magicNumber=0;

    for(int i=0; i<listSize; i++)
    {
        sum += list[i];
        magicNumber = sum /= 4;

    for(row=0; row<matrix.length; row++)
    {
            //sum each row, then compare to magicNumber
        for(col=0; col<matrix[row].length; col++)
        sumRow = sumRow + matrix[row][col];
        while (sumRow == magicNumber)
        {
            for(col=0; col<matrix.length; col++)
            {
                for(row=0; row<matrix[col].length; row++)
                {
                sumCol = sumCol + matrix[row][col];
                    while (sumCol == magicNumber)
                    {
                    sumDiag1 = matrix[0][0]+matrix[1][1]+matrix[2][2]+matrix[3][3];
                        while (sumDiag1 == magicNumber)
                        {
                        sumDiag2 = matrix[3][0]+matrix[2][1]+matrix[1][2]
                        +matrix[0][3];
                            while(sumDiag2 == magicNumber)
                            System.out.println("It is a magic square.");
                        }
                    }
                }
            }
        }
    }
    }
            System.out.println("It is not a magic square.");

}

public static void main (String [] args)
{
    int [] list = new int [listSize];
    createArithmeticSeq (list);
    int [] [] matrix = new int [rows] [columns];
    matricize(list, matrix);
    printMatrix(matrix);
    System.out.print("\n");
    reverseDiagonal(matrix);
    printMatrix(matrix);
    magicCheck(list, matrix);
}

}

最佳答案

当将listsize定义为static时，它将获得0的默认值。然后调用createArithmeticSeq(int [] list)，基本上是传递一个包含0个元素的空格的列表。创建listsize后，如果更改int [] list = new int [listSize];的值，则列表的大小不会改变。因此，您必须在知道数组的大小之后创建数组。

为此，将您的主要方法修改为

public static void main (String [] args)
{
    System.out.println("Enter size of array (in form nxn), n:");
    n = console.nextInt();
    rows = n;
    columns = n;
    listSize= (n*n);
    int [] list = new int [listSize];
    createArithmeticSeq (list);
    int [] [] matrix = new int [rows] [columns];
    matricize(list, matrix);
    printMatrix(matrix);
    System.out.print("\n");
    reverseDiagonal(matrix);
    printMatrix(matrix);
    magicCheck(list, matrix);
}

和您的createArithmeticSeq方法为

public static void createArithmeticSeq(int [] list)
{
    int first;
    int diff;
    //prompt user for first and diff
    System.out.println("Enter first and diff : ");
    first = console.nextInt();
    diff  = console.nextInt();
    //process to create list of n*n elements
    for (int i=0; i<listSize; i++)
    {
        list[i]=first+i*diff;
    }
}