使用Java读入一个TXT文件，文件中数据为字符串，数据之间使用空格隔开，n*n幻方，判断其行之和是否相等

以下为Java代码实现：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class MagicSquare {

    public static void main(String[] args) {
        int[][] square = readMagicSquare("magic_square.txt");
        if (isMagicSquare(square)) {
            System.out.println("This is a magic square.");
        } else {
            System.out.println("This is not a magic square.");
        }
    }

    public static int[][] readMagicSquare(String filename) {
        int[][] square = null;
        try (BufferedReader br = new BufferedReader(new FileReader(filename))) {
            String line = br.readLine();
            int n = line.split(" ").length;
            square = new int[n][n];
            int i = 0;
            while (line != null) {
                String[] nums = line.split(" ");
                for (int j = 0; j < n; j++) {
                    square[i][j] = Integer.parseInt(nums[j]);
                }
                line = br.readLine();
                i++;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return square;
    }

    public static boolean isMagicSquare(int[][] square) {
        int n = square.length;
        int sum = 0;
        for (int i = 0; i < n; i++) {
            sum += square[0][i];
        }
        // check row sum
        for (int i = 1; i < n; i++) {
            int rowSum = 0;
            for (int j = 0; j < n; j++) {
                rowSum += square[i][j];
            }
            if (rowSum != sum) {
                return false;
            }
        }
        // check column sum
        for (int i = 0; i < n; i++) {
            int colSum = 0;
            for (int j = 0; j < n; j++) {
                colSum += square[j][i];
            }
            if (colSum != sum) {
                return false;
            }
        }
        // check diagonal sum
        int diagSum1 = 0;
        int diagSum2 = 0;
        for (int i = 0; i < n; i++) {
            diagSum1 += square[i][i];
            diagSum2 += square[i][n - 1 - i];
        }
        if (diagSum1 != sum || diagSum2 != sum) {
            return false;
        }
        return true;
    }
}

其中，`readMagicSquare`方法用于读取文件中的幻方数据，返回一个二维数组。`isMagicSquare`方法用于判断该二维数组是否为幻方，即每行、每列、每条对角线的和均相等。如果是幻方，则返回`true`，否则返回`false`。最后，在`main`方法中调用这两个方法，输出结果。