How do I remove repeated elements from ArrayList?

To remove repeated elements from an ArrayList in Java, you can use the removeAll method and pass it a Collection containing the elements to be removed.

Here's an example:

import java.util.ArrayList;
import java.util.HashSet;

ArrayList<Integer> list = new ArrayList<>();

list.removeAll(new HashSet<>(list));

System.out.println(list); // [2, 3]

In this example, we create an ArrayList containing the elements 1, 2, 3, 2, and 1. We then use the removeAll method and pass it a HashSet containing the ArrayList to remove all duplicate elements. The HashSet is used to remove duplicates because it does not allow duplicate elements.

After the removeAll method is called, the ArrayList will contain only the unique elements 2 and 3.

Note: This method will remove all duplicate elements from the ArrayList, not just consecutive duplicates. If you want to remove only consecutive duplicates, you can use a different approach, such as iterating through the ArrayList and using the remove method to remove duplicates as you encounter them.