comparator java
// Java program to demonstrate working of Comparator
// interface
import java.util.*;
import java.lang.*;
import java.io.*;
// A class to represent a student.
class Student
{
int rollno;
String name, address;
// Constructor
public Student(int rollno, String name,
String address)
{
this.rollno = rollno;
this.name = name;
this.address = address;
}
// Used to print student details in main()
public String toString()
{
return this.rollno + " " + this.name +
" " + this.address;
}
}
class Sortbyroll implements Comparator<Student>
{
// Used for sorting in ascending order of
// roll number
public int compare(Student a, Student b)
{
return a.rollno - b.rollno;
}
}
class Sortbyname implements Comparator<Student>
{
// Used for sorting in ascending order of
// roll name
public int compare(Student a, Student b)
{
return a.name.compareTo(b.name);
}
}
// Driver class
class Main
{
public static void main (String[] args)
{
ArrayList<Student> ar = new ArrayList<Student>();
ar.add(new Student(111, "bbbb", "london"));
ar.add(new Student(131, "aaaa", "nyc"));
ar.add(new Student(121, "cccc", "jaipur"));
System.out.println("Unsorted");
for (int i=0; i<ar.size(); i++)
System.out.println(ar.get(i));
Collections.sort(ar, new Sortbyroll());
System.out.println("\nSorted by rollno");
for (int i=0; i<ar.size(); i++)
System.out.println(ar.get(i));
Collections.sort(ar, new Sortbyname());
System.out.println("\nSorted by name");
for (int i=0; i<ar.size(); i++)
System.out.println(ar.get(i));
}
}