利用二维int型数组表达一个矩阵，创建该数组并将其元素打印输出

public class ArrayOfArraysDemo1 {
    public static void main(String[] args) {
        int[][] aMatrix = new int[4][];

    //populate matrix
        for (int i = 0; i < aMatrix.length; i++) {
        aMatrix[i] = new int[5];    //create sub-array
        for (int j = 0; j < aMatrix[i].length; j++) {
            aMatrix[i][j] = i + j;
        }
        }

        //print matrix
        for (int i = 0; i < aMatrix.length; i++) {
        for (int j = 0; j < aMatrix[i].length; j++) {
            System.out.print(aMatrix[i][j] + " ");
        }
        System.out.println();
        }
    }
}