How do you sort an ArrayList in descending order?

[system]

Sorting an ArrayList in descending order in Java can be done using various approaches. The most common and straightforward way is by using the Collections.sort method along with a custom comparator or by using the sort method with a lambda expression. Here's how you can do it:

How to Sort an ArrayList in Descending Order:

1. Using Collections.sort with a Custom Comparator:

The Collections.sort method can be used with a custom comparator to sort the list in descending order.

   import java.util.ArrayList;
   import java.util.Collections;
   import java.util.Comparator;
public class SortArrayListDescending {  
public static void main(String args) {
ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(5);
list.add(30);

   // Using Collections.sort with a custom Comparator
   Collections.sort(list, new Comparator<Integer>() {
       @Override
       public int compare(Integer o1, Integer o2) {
           return o2.compareTo(o1);
       }
   });

   System.out.println("Sorted list in descending order: " + list);

}

}  

1. Using Collections.sort with a Lambda Expression:

A more concise way to achieve the same result is by using a lambda expression.

   import java.util.ArrayList;
   import java.util.Collections;
public class SortArrayListDescending {  
public static void main(String args) {
ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(5);
list.add(30);

   // Using Collections.sort with a lambda expression
   Collections.sort(list, (a, b) -> b - a);

   System.out.println("Sorted list in descending order: " + list);

}

}  

1. Using the sort Method with a Lambda Expression:

Java 8 introduced the sort method for the List interface, which can also be used with a lambda expression.

   import java.util.ArrayList;
public class SortArrayListDescending {  
public static void main(String args) {
ArrayList<Integer> list = new ArrayList<>();
list.add(10);
list.add(20);
list.add(5);
list.add(30);

   // Using the List's sort method with a lambda expression
   list.sort((a, b) -> b - a);

   System.out.println("Sorted list in descending order: " + list);

}

}