What is the main difference between comparable and comparator?

Difference between Comparable vs Comparator in Java
Comparable Comparator
The class whose objects you want to sort must implement comparable interface. Class, whose objects you want to sort, do not need to implement a comparator interface.
It provides single sorting sequences. It provides multiple sorting sequences.
Apr 25, 2021

What is the difference between comparator and comparable in Java examples?

For example Roll Numbers of students. Whereas, Comparator interface sorting is done through a separate class. Logically, Comparable interface compares “this” reference with the object specified and Comparator in Java compares two different class objects provided.

Why do we use comparable and comparator in Java?

Comparable v/s Comparator in Java

Comparable interface is used to sort the objects with natural ordering. Comparator in Java is used to sort attributes of different objects. Comparable interface compares “this” reference with the object specified. Comparator in Java compares two different class objects provided.

How do you sort an object using comparator and comparable?

We had to override the compareTo() method twice for the same logic. If there were more elements we would have to replicate the logic for each object. These examples demonstrate the main difference between Comparable and Comparator . Use Comparable when there is a single, default comparison for your object.

Which is the use of comparator?

A comparator circuit compares two voltages and outputs either a 1 (the voltage at the plus side) or a 0 (the voltage at the negative side) to indicate which is larger. Comparators are often used, for example, to check whether an input has reached some predetermined value.

How do you sort an ArrayList in alphabetical order?

To sort the ArrayList, you need to simply call the Collections. sort() method passing the ArrayList object populated with country names. This method will sort the elements (country names) of the ArrayList using natural ordering (alphabetically in ascending order).

Does ArrayList maintain insertion order?

ArrayList maintains the insertion order i.e order of the object in which they are inserted. HashSet is an unordered collection and doesn’t maintain any order. ArrayList allows duplicate values in its collection.

How do you sort an ArrayList?

How to sort an ArrayList in Java in descending order?
  1. Create an ArrayList.
  2. Sort the contents of the ArrayList using the sort() method of the Collections class.
  3. Then, reverse array list using the reverse() method of the Collections class.

How do you sort objects in ArrayList?

ArrayList sort() method sorts the list according to the order induced by the specified Comparator instance.

2. ArrayList sort() – Sort list of objects by field

  1. 2.1. Employee Class.
  2. 2.2. Comparator classes to enable sorting on different fields.
  3. 2.3. ArrayList sort() example.

How do you sort list by ID?

In that case, implement the Comparator interface in the custom class. For example, the domain object Employee has a custom corasion logic based on the employee id field. Checkout for comparison logic in compareTo() method. Java program to sort the list of employee objects by id , in ascending and descending orders.

How do you compare elements in an ArrayList?

There are following ways to compare two ArrayList in Java:
  1. Java equals() method.
  2. Java removeAll() method.
  3. Java retainAll() method.
  4. Java ArrayList. contains() method.
  5. Java contentEquals() method.
  6. Java Stream interface.