Example of Comparable and Comparator interface and how they work

comparable_comparator.java

//Package removed
import java.util.*;
import java.io.*;
import java.lang.*;
import java.math.*;
class Test{
	
	public static void main(String[] args) {
    //list to store people objects
		List<Person> people=new ArrayList<Person>();
		people.add(new Person("prakash", 21, 1200000));
		people.add(new Person("harry", 22, 900000));
		people.add(new Person("mohit", 28, 1800000));
		people.add(new Person("rahul", 24, 4000000));
		Collections.sort(people);
		for(Person p : people){
			System.out.println(p.name+" "+p.age+" "+p.salary);
		}
		System.out.println("-----------using comparator------------");
		System.out.println("using age : ");
		setAge ageOrder=new setAge();
		Collections.sort(people, ageOrder);
		for(Person p : people){
			System.out.println(p.name+" "+p.age+" "+p.salary);
		}
		System.out.println("using name : ");
		setName nameOrder=new setName();
		Collections.sort(people, nameOrder);
		for(Person p : people){
			System.out.println(p.name+" "+p.age+" "+p.salary);
		}
		System.out.println("using salary : ");
		setSalary salaryOrder=new setSalary();
		Collections.sort(people, salaryOrder);
		for(Person p : people){
			System.out.println(p.name+" "+p.age+" "+p.salary);
		}
		
	}
	

}
class Person implements Comparable<Person>{ 
	public String name;
	public String getName() {
		return name;
	}
	
	public int getAge() {
		return age;
	}
	
	public int getSalary() {
		return salary;
	}
	
	public int age;
	public int salary;
	public Person(String nm, int ag, int sal){
		this.name=nm;
		this.age=ag;
		this.salary=sal;
	}
	
	public int compareTo(Person o) {
		return (this.salary-o.salary);
	}
	
}
class setAge implements Comparator<Person>{

	
	public int compare(Person o1, Person o2) {
		if(o1.getAge()>o2.getAge()){
			return 1;
		}
		else if(o1.getAge()<o2.getAge()){
			return -1;
		}
		return 0;
	}
	
}
class setSalary implements Comparator<Person>{

	
	public int compare(Person o1, Person o2) {
		if(o1.getSalary()>o2.getSalary()){
			return 1;
		}
		else if(o1.getSalary()<o2.getSalary()){
			return -1;
		}
		return 0;
		
	}
	
}
class setName implements Comparator<Person>{

	
	public int compare(Person o1, Person o2) {
		
		return (o1.getName().compareTo(o2.getName()));
	}
	
}