Problem 9. ListOfProducts - Java Loops, Method, Classes.

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Collections;


public class _09_ListOfProducts {
    public static void main(String[] args) {
        ArrayList<Product> products = new ArrayList<>();

        try {
            BufferedReader fileReader = new BufferedReader(new FileReader("src/input1.txt"));
            File fileProducts = new File("src/products.txt");
            fileProducts.createNewFile();
            BufferedWriter fileWriter = new BufferedWriter(new FileWriter("src/products.txt"));
            while (true) {
                String line = fileReader.readLine();
                if (line == null) {
                    fileReader.close();
                    break;
                }
                String[] input = line.split(" ");
                products.add(new Product(input[0], new BigDecimal(input[1])));
            }
            Collections.sort(products);
            for (Product product : products) {
                System.out.println(product.getName() + " " + product.getPrice());
                fileWriter.write(product.getName() + " " + product.getPrice());
                fileWriter.newLine();
            }
            fileWriter.close();
        }catch (IOException e) {
            System.out.println("Error!");
        }
    }

}

class Product implements Comparable<Product> {
    private String name;
    private BigDecimal price;

    public Product(String name, BigDecimal price) {
        super();
        this.name = name;
        this.price = price;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public BigDecimal getPrice() {
        return price;
    }
    public void setPrice(BigDecimal price) {
        this.price = price;
    }
    public int compareTo(Product compareProduct) {

        BigDecimal comparePrice = ((Product)compareProduct).getPrice();

        //ascending order
        return this.price.compareTo(comparePrice);

        //descending order
        //return comparePrice.compareTo(this.price);

    }
}