In Advance Java, Comparable and Comparator are used to define custom sorting logic for objects. They help Java collections like Collections.sort() and TreeSet decide how objects should be ordered.
? Key Concepts
Comparable defines natural ordering inside the class itself
Comparator defines external ordering outside the class
Both are part of java.util package
Used mainly with Collections and sorting algorithms
? Syntax / Theory
Comparable → compareTo(Object o)
Comparator → compare(Object o1, Object o2)
Comparable supports only one sorting logic
Comparator supports multiple sorting strategies
? Code Example — Comparable
? View Code Example
// Student class implementing Comparable
class Student implements Comparable {
int id;
String name;
Student(int id, String name) {
this.id = id;
this.name = name;
}
public int compareTo(Student s) {
// Sort students by id in ascending order
return this.id - s.id;
}
}
? Code Example — Comparator
? View Code Example
// Comparator to sort students by name
import java.util.Comparator;
class NameComparator implements Comparator {
public int compare(Student s1, Student s2) {
// Compare student names alphabetically
return s1.name.compareTo(s2.name);
}
}
? Sorting Simulator
Click the buttons to see how the list changes based on logic.
? Live Output / Explanation
What Happens?
Using Comparable sorts students by id
Using Comparator sorts students by name
Comparator does not modify the Student class
✅ Tips & Best Practices
Use Comparable when there is a single natural order
Use Comparator for flexible or multiple sorting rules
Avoid complex logic inside compareTo()
Prefer Comparator in real-world applications
? Try It Yourself
Create a Comparator to sort students by name length