int[][] nums = new int[3][];
nums[0] = new int[1];
nums[1] = new int[2];
nums[2] = new int[3];
int[][] foo = new int[][] {
new int[] { 1, 2, 3 },
new int[] { 1, 2, 3, 4},
};
System.out.println(foo.length); //2
System.out.println(foo[0].length); //3
System.out.println(foo[1].length); //4