# How to swap rows and columns of a 2d array?

I’m trying to write a method for ‘transpose’ a two-dimensional array of integers, in which the rows and columns of the original matrix are exchanged.

However, I have no idea how I can realize this. How do I write out this method?

```public class Matrix {
private int[][] numbers;

public Matrix(int rows, int colums) {
if (rows < 1)
rows = 1;
else
rows = rows;
if (colums < 1)
colums = 1;
else
colums = colums;
numbers = new int[rows][colums];
}

public final void setNumbers(int[][] numbers) {
this.numbers = numbers;
}

public int[][] getNumbers() {
return numbers;
}

public int[][] transpose() {
int[][] transpose = getNumbers();
return numbers;
}
}
```

You could iterate over the rows and columns and assign each element [i,j] to the transposed [j,i]:

```/**
* Transposses a matrix.
* Assumption: mat is a non-empty matrix. i.e.:
* 1. mat != null
* 2. mat.length > 0
* 3. For every i, mat[i].length are equal and mat[i].length > 0
*/
public static int[][] transpose(int[][] mat) {
int[][] result = new int[mat.length][mat.length];
for (int i = 0; i < mat.length; ++i) {
for (int j = 0; j < mat.length; ++j) {
result[j][i] = mat[i][j];
}
}
return result;
}
```
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