I want to order only one list and java is ordering both of them

Question

I am new at Java and I am trying to sort a list called rojas who has been copied from list. When using arrays.sort and then printing it, I realized that both rojas and list are getting sorted.

public static void main(String[] args) {
    int[] list = {611, 700, 777, 901, 4124, 8000, 9014, 6213113, 15, 19, 100, 102, 150, 177, 310, 330, 400, 590, 600};

    int[] rojas = list;

    int size = 20;
    int value = 100;

    for (int i=0 ;i< size-1; i++){
        if(list[i] == value){
           System.out.println("Element found index is :"+ i);
           break;
        }
        else{
           System.out.println("Element not found");}
        
    }

    Arrays.sort(rojas);
    System.out.println("element found by binary search is in index: " + Arrays.binarySearch(rojas,100));

    System.out.println(Arrays.toString(rojas));
    System.out.println(Arrays.toString(list));
}

1. What you have is not a List but an array 2. You only have 1 array object, but 2 variables `list` and `rojas` pointing at that one single array. In java objects don't get automatically cloned when you assign them to variables. If you want to make a copy of your 1 array so that you have 2 arrays [you need to create that copy yourself](https://stackoverflow.com/questions/5785745/make-copy-of-an-array) — OH GOD SPIDERS, Oct 14 '22 at 14:40

score 1 · Answer 1 · answered Oct 14 '22 at 14:56

1

Copy the value of the array instead of the reference.

It should be

int[] rojas = Arrays.copyOf(list, list.length);

answered Oct 14 '22 at 14:56

Ankit Sharma

1,626
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14
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score 0 · Answer 2 · answered Oct 14 '22 at 14:40

0

Are you sure the list has been copied?

There is one list with two references. So sorting either variable will sort the single underlying list

answered Oct 14 '22 at 14:40

Asad Awadia

1,417
2
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15

score 0 · Answer 3 · answered Oct 14 '22 at 14:56

As mentioned in the comments, there is only one array (not list) with two references / variables, and therefore when the array is sorted using one reference, the other variables refers the sorted array.

You should create a copy / clone the original array, which can be done like this:

int[] rojas = list.clone();

int[] rojas2 = Arrays.copyOf(list, list.length);

score 0 · Answer 4 · answered Oct 14 '22 at 14:56

0

You copy the reference, not the value, as Asad Awadia mentioned.

You can do the following to create a new Array:

int[] rojas = list.clone();

answered Oct 14 '22 at 14:56

Christoph S.

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I want to order only one list and java is ordering both of them

4 Answers4