new Array(matrix.length) code example

Example: 2d array length in java

public static void main(String[] args) {

    int[][] foo = new int[][] {
        new int[] { 1, 2, 3 },
        new int[] { 1, 2, 3, 4},
    };

    System.out.println(foo.length); //2 // gives count of rows
    System.out.println(foo[0].length); //3 // gives count of columns for particular row
    System.out.println(foo[1].length); //4
}