Java: Convert List to primitive Array long[] ; and primitive Array long[] to List

For instance, you have a list of Long object.

        List<Long> list = <your list>;

You want to convert it to a long[].

1. Java 8
 
        Convert the list to a Stream<Long>, map each Long object to long, and then convert the result to an array.

        long[] array = list.stream().mapToLong(Long::longValue).toArray();

2. Before Java 8 versions

        Created an empty array with the size of your list, loop through the list and add each element to the array.

         long [] array = new long[list.size()];
         int i = 0;
         for (long element : list) {
                 array[i++] = element;
         }

Now you have a long[] array2 object and you want to convert it to a List<Long> object.

3. Java 8

        List<Long> list2 = Arrays.stream(array2).boxed().collect(Collectors.toList());

4. Before Java 8 versions.

        List<Long> list2 = new ArrayList<>();
        for (long value : array2) {
                list2.add(new Long(value));
        }

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