array print from function - java

Question

I am trying to print an array of some prime numbers which are divided by a number, the output I get for this code:

[J@15db9742

How can I print the array I get by the function.

public static long[] primes(int n) {
    int count = 0;
    long arr1[] = new long[n];
    for (int i = 2; i < n; i++) {
        boolean prime = true;
        if (n % i == 0)
            for (int j = 2; j < i && prime; j++) {
                if (i % j == 0) prime = false;
            }
        if (prime && n % i == 0) {
            arr1[count] = i;
            System.out.println(arr1[count]);
            count++;
        }
    }

    long arr[] = new long[count];
    for (int i = 0; i < arr.length; i++) {
        arr[i] = arr1[i];
    }
    return arr;
}

`System.out.println(Arrays.toString(arr));` – Paul Boddington Mar 27 '15 at 21:03 — Paul Boddington, Mar 27 '15 at 21:03
@pbabcdefp answer is the best. – Soham Mar 27 '15 at 21:08 — Soham, Mar 27 '15 at 21:08

catch23 · Answer 1 · 2015-03-27T21:36:05.217

4

Array is reference type.

And you have to use utility class Arrays for printing arrays:

Arrays.toString(array)

for multidimensional arrays:

Arrays.deepToString(array)

BTW
Small suggestions you can use some optimization instead for loop:

    for (int i = 0; i < arr.length; i++) {
        arr[i] = arr1[i];
    }

better to use System.arraycopy():

System.arraycopy(arr1, 0, arr, 0, arr.length);

edited Mar 27 '15 at 21:36

answered Mar 27 '15 at 21:06

catch23

17,519
42
144
217

Or, just `return arr1.clone()`. – Louis Wasserman Mar 27 '15 at 21:31
@LouisWasserman It will work, but for ***multidimensional arrays*** `clone()` fails. – catch23 Mar 27 '15 at 21:35
If this problem involved multidimensional arrays, I wouldn't have suggested it? But this question doesn't seem to need generalization to multidimensional arrays. (Also, `System.arraycopy` doesn't work any better for multidimensional arrays.) – Louis Wasserman Mar 27 '15 at 21:37
@LouisWasserman `arr1` and `arr` have different lengths so `clone` won't work. – Paul Boddington Mar 27 '15 at 21:44
@pbabcdefp: Ah, I follow, good catch. Then you want `Arrays.copyOf(arr1, count)`. – Louis Wasserman Mar 27 '15 at 21:45

score 0 · Answer 2 · answered Mar 27 '15 at 21:06

0

for(long n: arr)
 System.out.println(n);

answered Mar 27 '15 at 21:06

Soham

4,397
11
43
71

array print from function - java

2 Answers2