Copy of array to use in several methods java

Question

I'm learning java and my program uses the sorting algorithms. The user can choose the size of the array. I learned to copy an array thanks to this question: Make copy of array Java

I copy the array like this:

    public static void main(String[] args) {
    int num = Integer.parseInt(JOptionPane.showInputDialog("Size of the array: ?"));
    int [] list = new int[num];
    for(int i=0;i<num;i++){
        int num2 = Integer.parseInt(JOptionPane.showInputDialog("Element: "+(i+1)));
        list[i]=num2;
    }
    int [] listCopy = Arrays.copyOf(list, list.length);

For my bubblesort I used the array saved inside list, for my selection sort I used the array saved inside my listCopy but when I tried to use the insertion sort with listCopy, the array was already sorted.

How can I copy an array so it never changes?

Can you please share the code for your bubble and insertion sorts? It's kind of hard to understand the issue without seeing the actual code. — Mureinik, Sep 21 '14 at 18:19
@Mureinik I think he has sorted the arrays that he already has i.e. `list` and `listCopy` with 2 algorithm. He is new to programming and want to sort array with all his algos. — afzalex, Sep 21 '14 at 18:23

score 1 · Accepted Answer · answered Sep 21 '14 at 18:25

A copy of an array is simply another array, which behaves the same way as any other array: when you pass a copy to a sorting method, the copy becomes sorted, and remains sorted after that.

If you need to pass an unsorted array to multiple methods, make new copies as you go, like this:

int [] orig = new int[num];
for(int i=0;i<num;i++){
    int num2 = Integer.parseInt(JOptionPane.showInputDialog("Element: "+(i+1)));
    orig[i]=num2;
}
int [] copy = Arrays.copyOf(orig, orig.length);
bubbleSort(copy);
printArray(copy);
copy = Arrays.copyOf(orig, orig.length);
selectionSort(copy);
printArray(copy);
copy = Arrays.copyOf(orig, orig.length);
insertionSort(copy);
printArray(copy);

score 1 · Answer 2 · answered Sep 21 '14 at 18:25

1

You cannot create an immutable array, however you can create an immutable list:

List<Integer> immutableList = Collections.unmodifiableList(Arrays.asList(array));

answered Sep 21 '14 at 18:25

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Copy of array to use in several methods java

2 Answers2