Comparator vs Comparable in Java

Comparable?is used at the?class level in Java, while Comparator is used at the object level.

? Comparable (Class-Level)

• Implements Comparable<T> inside the class.
• Uses the internal method compareTo(T o).
• Return Type: int (0 if equal, positive if greater, negative if smaller).
• Parameter: One object (T o).
• Defines a natural ordering.
• Swapping happens when compareTo() returns > 0.

?? Example:

class Student implements Comparable<Student> {  
    int id;  
    String name;  

    public Student(int id, String name) {  
        this.id = id;  
        this.name = name;  
    }  

    @Override  
    public int compareTo(Student other) {  
        return Integer.compare(this.id, other.id);  
    }  
}
        

? Comparator (Object-Level)

• Uses Comparator<T> as an external method.
• Uses the internal method compare(T o1, T o2).
• Return Type: int (same as Comparable).
• Parameter: Two objects (T o1, T o2).
• Defines custom sorting.
• Swapping happens when compare() returns > 0.

?? Example:

import java.util.Comparator;  

class StudentNameComparator implements Comparator<Student> {  
    @Override  
    public int compare(Student s1, Student s2) {  
        return s1.name.compareTo(s2.name);  
    }  
}
        

?? Check my GitHub for full implementation: [GitHub link]

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