What is the purpose of the Comparable interface in Java?

The Comparable interface is used to define the natural ordering of objects of a class. Classes that implement this interface can be sorted without explicitly specifying a comparator.

The compareTo(T o) method:

• Returns a negative integer if the current object is less than the specified object.
• Returns a positive integer if the current object is greater than the specified object.
• Returns zero if the objects are equal.

Example implementation:

public class MyClass implements Comparable<MyClass> {
    private int value;

    public MyClass(int value) {
        this.value = value;
    }

    @Override
    public int compareTo(MyClass other) {
        // Comparison based on the value field
        return Integer.compare(this.value, other.value);
    }

    // Getters, setters, equals, hashCode, etc.
}

Using with collections:

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

public class SortingExample {
    public static void main(String[] args) {
        List<MyClass> list = new ArrayList<>();
        list.add(new MyClass(5));
        list.add(new MyClass(2));
        list.add(new MyClass(8));

        // Sorting using the natural order
        Collections.sort(list);

        // Now the objects in the list are sorted in ascending order of value
        for (MyClass obj : list) {
            System.out.println(obj.value);
        }
    }
}