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

class 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 String toString() {return product_name+"("+part_number+")";}
}

class Main
{
	public static void main(String[] args)
	{
		Set<Product> parts = new HashSet<>(); // OK: HashSet, Error: TreeSet
		
		parts.add(new Product("Widget", 4562));
		parts.add(new Product("Toaster", 1234));
		parts.add(new Product("Modem", 9912));
		System.out.println(parts);
		
	}
}

/*
implements Comparable<Product>
public int compareTo(Product other) {return Integer.compare(part_number,  other.part_number);}
 */