how to reorder numbers in a list randomly in java

To reorder the elements of a List in Java randomly, you can use the Collections.shuffle method of the java.util.Collections class. This method shuffles the elements of the List in place using a default random number generator.

Here is an example of how you can use the Collections.shuffle method to shuffle the elements of a List in Java:

import java.util.Collections;
import java.util.List;

List<Integer> list = List.of(1, 2, 3, 4, 5);
Collections.shuffle(list);

System.out.println(list);  // Outputs a shuffled list, such as "[5, 2, 4, 1, 3]"

In this example, the Collections.shuffle method is called on the listList object, and it shuffles the elements of the list in place using a default random number generator.

Keep in mind that the Collections.shuffle method operates on the original List object and shuffles the elements in-place, without creating a new List. If you want to create a new List with the elements shuffled, you can use the stream API or the collect method of the Stream interface to create a new List from the shuffled elements.

For example:

import java.util.List;
import java.util.stream.Collectors;

List<Integer> list = List.of(1, 2, 3, 4, 5);
List<Integer> shuffledList = list.stream().collect(Collectors.toList());
Collections.shuffle(shuffledList);

System.out.println(shuffledList);  // Outputs a shuffled list, such as "[5, 2, 4, 1, 3]"

You can also use the shuffle method of the List interface (which is implemented by various classes such as ArrayList and LinkedList) to shuffle the elements of a List. This method shuffles the elements of the List in place using a specified random number generator.

For example:

import java.util.List;
import java.util.Random;

List<Integer> list = List.of(1, 2, 3, 4, 5);
Random random = new Random();
list.shuffle(random);

System.out.println(list);  // Outputs a shuffled list, such as "[5, 2, 4, 1, 3]"

In this example, the shuffle method is called on the listList object, and it shuffles the elements of the list in place using a specified Random object.