转置数组无法正确打印

Question

I'm trying to print the transposed version of this matrix array but it is instead printing the memory locations. Any input on how to print the actual array?

This is what it prints: [[I@4b71bbc9, [I@17dfafd1, [I@5e8fce95]

    import java.util.*;

class MatrixTranspose
{
    public static void main (String [] args)
    {
        int [] [] m = {
                    {3, 6, 9},
                    {4, 1, 5},
                    {5, 8, 7},              
                };

         System.out.println (Arrays.toString (transpose(m)));       
    }

    public static int [] [] transpose (int [] [] x)
    {
        int start = 1;

        for (int r = 0; r < x.length; r++)
        {
            for (int c = start; c < x[0].length; c++)
            {
                int temp = x[r][c];
                x [r][c] = x[c][r];
                x[c][r] = temp;
            }

            start++;
        }

        return x;
    }
}

Answer 1

transpose(int[][] x) returns a 2-dimensional array.

Use Arrays.deepToString(Object[] a) instead :

If an element e is an array of a primitive type, it is converted to a string as by invoking the appropriate overloading of Arrays.toString(e) . If an element e is an array of a reference type, it is converted to a string as by invoking this method recursively.

System.out.println(Arrays.deepToString(transpose(m)));  

Answer 2

Use Arrays#deepToString instead.

In Java, each object has toString() method, the default is displaying the class name representation, then adding @ and then the hashcode.

To better understand the output you're getting, see the implementation of Arrays#toString :

3860     public static String toString(int[] a) { {
3861        if (a == null)
3862            return "null";
3863        int iMax = a.length - 1;
3864        if (iMax == -1)
3865            return "[]";
3866
3867        StringBuilder b = new StringBuilder();
3868        b.append('[');
3869        for (int i = 0; ; i++) {
3870            b.append(a[i]);
3871            if (i == iMax)
3872                return b.append(']').toString();
3873            b.append(", ");
3874        }
3875    }

the toString is applied on an array , resulting the "weird" output you got.