K&B , Chap1 Q11

Below question is from K&B book Chap 1, Q11
Given the following,
1. public class Test {
2. public static void main(String [] args) {
3. int [] [] [] x = new int [3] [] [];
4. int i,j;
5. x[0] = new int[4][];
6. x[1] = new int[2][];
7. x[2] = new int[5][];
8. for (i=0; i<x.length; i++)
9. for (j=0; j<x[i].length; j++) {
10. x[i][j] = new int [i + j + 1];
11. System.out.println("size = " + x[i][j].length);
12. }
13.

how many lines of output will be produced? (Choose one.)
A. 7
B. 9
C. 11
D. 13
E. Compilation fails
F. An exception is thrown at runtime

Answer C.

Author nicely escapes without giving a explanation on this question

Can someone explain , how it works

I haven't run this example, but the loops sound to work like that. The loop with variable i, (outer loop) runs for three iterations as the first dimension of x array is 3, for each iteration, the inner loop iterates for 4, 2 and 5 times so total iterations are 11. I hope you can understand how inner loop is iterated for each individual size mentioned for 2nd dimension of x-array.

Awww,

Author nicely escapes without giving a explanation on this question

I thought our "explanation" was pretty useful

Bert

2. public static void main(String [] args) {
3. int [] [] [] x = new int [3] [] [];
// Here an array of size 3 is created. Each element in the array is an
array which contains an array of ints.

4. int i,j;
5. x[0] = new int[4][];
// The first entry in the array referred to by x is set to an array containing 4 int arrays.

6. x[1] = new int[2][];
// The second entry in the array referred to by x is set to an array containing 2 int arrays.

7. x[2] = new int[5][];
// The third entry in the array referred to by x is set to an array containing 5 int arrays.

8. for (i=0; i<x.length; i++)
9. for (j=0; j<x[i].length; j++) {
10. x[i][j] = new int [i + j + 1];
11. System.out.println("size = " + x[i][j].length);
12. }
13.

// The outer loop here executes 3 times. On the first pass, a loop of length 4 is run. On the second pass, a loop of length 2 is run. On the third pass, a loop of length 5 is run.

So you have 11 runs. Each time you print a line.

Hi ,

MuraliRam Narasimhan has mentioned the name of the book as k&b , is it
khalid mughal's book for scjp. I am a new one in this forum, so pls let
me know.

Thanks,
Sumit

Its certification book by Kathy Sierra, Bert Bates

hi...the only way to solve questions "involving dynamic initialization of arrays using fo loops" is to dray a picture of the array. its a piece of cake then

bye

Keith, your explanation is good, but for a minor (major?) detail.
Each element in the x int array refers to an array of ints and not an array of int arrays, which would make x a 3D array.
Sashi

But isn't it the case that

int[] x -> x refers to an array of ints

int[][] x -> x refers to an array of arrays of ints

int[][][] x -> x refers to an array of arrays of arrays of ints

Sashi, I concur with Keith:

The original declaration int[][][] x means that each element of the array x is an int[][].

Well, I came, I saw, I concurred.
Sashi

Number of lines of o/p = 4+2+5 = 11

[Sashi]: Well, I came, I saw, I concurred