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Explanation

Comparator is an interface in the java.util package used to define custom sorting logic for objects. It is used when you want multiple sorting strategies.

Code:

public interface Comparator<T> {
    int compare(T o1, T o2);
}

Explanation

Comparator is used to sort objects based on different fields such as name, salary, or age without modifying the original class.

Code:

Collections.sort(list, new NameComparator());

Explanation

Example of sorting Student objects by name using Comparator.

Code:

Explanation

Code:

import java.util.*;
class Student {
    int id;
    String name;
    Student(int id, String name) {
        this.id = id;
        this.name = name;
    }
}
class NameComparator implements Comparator<Student> {
    public int compare(Student s1, Student s2) {
        return s1.name.compareTo(s2.name);
    }
}

Explanation

Comparator can also be implemented using lambda expressions in Java 8 and above.

Code:

Collections.sort(list, (s1, s2) -> s1.name.compareTo(s2.name));