how to rotate a matrix 90 degrees clockwise in java (Function)

/**
 * @author lautturi.com 
 * Java example: rotate a matrix 90 degrees clockwise in java (Function)
 */

import java.util.*;

public class Lautturi {
   // rotate a matrix 90 degrees clockwise in java  
	static int[][] rotateMatrix(int[][] matrix) {
		if(matrix == null) 
			return null;
		int rows = matrix.length;
		int cols = rows > 0 ? matrix[0].length : 0;
		if (rows == 0 || cols == 0)
			return null;
		int[][] newMatrix = new int[cols][rows];

		for (int i = 0; i < cols; i++) {
			for (int j = 0; j < rows; j++) {
				newMatrix[i][j] = matrix[j][i];

			}
			reverseArray(newMatrix[i]);
		}
		return newMatrix;
	}

	static void reverseArray(int[] arr) {
		for (int i = 0; i < arr.length / 2; i++) {
			int temp = arr[i];
			arr[i] = arr[arr.length - i - 1];
			arr[arr.length - i - 1] = temp;
		}
	}

	public static void main(String[] args) {
		int matrix[][] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 } };
		
		// print the matrix/2d-array in java
		for (int[] subarray : matrix) {
			for (int element : subarray) {
				System.out.printf("%5d", element);
			}
			System.out.println();
		}
		
// rotate a matrix 90 degrees clockwise in java  
		int[][] newMatrix = rotateMatrix(matrix);
//		if(newMatrix != null) {
//			
//		}
		System.out.println("-----new Matrix--------");
		// print the matrix/2d-array in java
		for (int[] subarray : newMatrix) {
			for (int element : subarray) {
				System.out.printf("%5d", element);
			}
			System.out.println();
		}

	}
}

output:

1    2    3    4
    5    6    7    8
    9   10   11   12
-----new Matrix--------
    9    5    1
   10    6    2
   11    7    3
   12    8    4