[Java] Shallow copy and deep copy when converting an array to List

There are the following two methods to create a List object from an existing array.

  1. Use ```Arrays.asList (array) `` `
  2. Use the constructor of a List implementation class such as ArrayList

Arrays.asList(Array)If you use, it will be a shallow copy and you just pass the reference.

```arraylist```When using the constructor of list implementation class such as, it will be a new replication.

### Arrays.asList
 Just pass the reference as a shallow copy.

        // Arrays.asList()Just pass a reference
        String[] ary = {"a", "b", "c"};
        List<String> list = Arrays.asList(ary);
        //  list.add("d"); // => java.lang.UnsupportedOperationException
        list.set(0, "e");
        System.out.println(Arrays.toString(ary)); //=> [e, b, c]The original layout has also changed.
        System.out.println(list);                 //=> [e, b, c]

It is possible to change the element with set, but be careful because an error will occur if you change the structure of an existing array such as add.

List implementation class constructor

It will be a new copy.

        //Create a new one by instantiating it with an implementation class of List such as ArrayList
        String[] ary2 = {"a", "b", "c"};
        List<String> list2 = new ArrayList<>(Arrays.asList(ary2));
        list2.set(0, "e");
        System.out.println(Arrays.toString(ary2)); //=> [a, b, c]The original array is unchanged.
        System.out.println(list2);                 //=> [e, b, c, d]

Since new ArrayList <> (array) cannot be done, it is necessary to convert it to List object once.

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