import java.io.*;
import java.util.*;

class Product implements Comparable<Product>
{
	private int part_number; //sometimes we want to compare part_number
	private String product_name; //sometimes we want compare product name
	public Product(String name,int num) {
		part_number=num;
		product_name=name;
	}
	public String getName() {return product_name;}
	public int compareTo(Product other) {return Integer.compare(part_number,  other.part_number);}
	public String toString() {return product_name+"("+part_number+")";}
}

public class Main
{
	public static void main(String[] args)
	{
		SortedSet<Product> parts = new TreeSet<>();
		//Set<Product> parts = new TreeSet<>(); //OK
		//SortedSet<Product> parts = new HashSet<>();  //Error: HashSet does not keep items sorted => cannot be SortedSet
		
		parts.add(new Product("Widget", 4562));
		parts.add(new Product("Toaster", 1234));
		parts.add(new Product("Modem", 9912));
		System.out.println(parts);

		SortedSet<Product> sortByName = new TreeSet<>( new
				Comparator<Product>()
				{
					public int compare(Product a, Product b)
					{
						String descrA = a.getName();
						String descrB = b.getName();
						return descrA.compareTo(descrB);
					}
				}
		);

		sortByName.addAll(parts);
		System.out.println(sortByName);
	}
}