顺时针打印矩阵

import java.util.*;


public class test {
    public static void main(String[] args) {
        //[[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]]
        int[][] matrix = {{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}};
        ArrayList<Integer> integers = null;
        try {
            integers = printMatrix(matrix);
        } catch (Exception e) {
            e.printStackTrace();
        }
        for (int i = 0; i < integers.size(); i++) {
            System.out.print(integers.get(i) + ",");
        }
    }


    public static ArrayList<Integer> printMatrix(int[][] matrix) {
        ArrayList<Integer> resultList = new ArrayList<>();
        int rows = matrix.length;
        int columns = matrix[0].length;
        if (matrix == null) {
            return null;
        }
        int start = 0;
        //循环打印每一圈
        while (columns > start * 2 && rows > start * 2) {
            ArrayList<Integer> circleList = printMatrixInCircle(matrix, columns, rows, start);
            resultList.addAll(circleList);
            ++start;
        }
        return resultList;
    }

    public static ArrayList<Integer> printMatrixInCircle(int[][] matrix, int columns, int rows, int start) {
        ArrayList<Integer> circleList = new ArrayList<>();
        int endX = columns - 1 - start;//终止列号
        int endY = rows - 1 - start;//终止行号
        //从左到右打印
        for (int i = start; i <= endX; i++) {
            int number = matrix[start][i];
            circleList.add(number);
        }
        //从上到下打印
        if (start < endY) {
            for (int i = start + 1; i <= endY; i++) {
                int number = matrix[i][endX];
                circleList.add(number);
            }
        }

        //从右向左打印
        if (start < endX && start < endY) {
            for (int i = endX - 1; i >= start; i--) {
                int number = matrix[endY][i];
                circleList.add(number);
            }
        }

        //从下到上打印
        if (start < endX && start < endY - 1) {
            for (int i = endY - 1; i >= start + 1; i--) {
                int number = matrix[i][start];
                circleList.add(number);
            }
        }
        return circleList;
    }

}