Add appropriate descriptive comments to each line of code in the project explaining why the code is in the application.

package murach.db;

import java.io.*; import java.nio.file.*; import java.util.*;

import murach.business.Product;

public final class ProductTextFile implements DAO { private List products = null; private Path productsPath = null; private File productsFile = null; private final String FIELD_SEP = "\t";

public ProductTextFile() { productsPath = Paths.get("products.txt"); productsFile = productsPath.toFile(); products = this.getAll(); }

@Override public List getAll() { if (products != null) { return products; }

products = new ArrayList<>(); if (Files.exists(productsPath)) { try (BufferedReader in = new BufferedReader( new FileReader(productsFile))) {

String line = in.readLine(); while (line != null) { String[] fields = line.split(FIELD_SEP); String code = fields[0]; String description = fields[1]; String price = fields[2];

Product p = new Product( code, description, Double.parseDouble(price)); products.add(p);

line = in.readLine(); } } catch (IOException e) { // System.out.println(e); return null; } } else { // System.out.println(productsPath.toAbsolutePath() + " doesn't exist."); return null; } return products; }

@Override public Product get(String code) { for (Product p : products) { if (p.getCode().equals(code)) { return p; } } return null; }

private boolean saveAll() { try (PrintWriter out = new PrintWriter( new BufferedWriter( new FileWriter(productsFile)))) {

for (Product p : products) { out.print(p.getCode() + FIELD_SEP); out.print(p.getDescription() + FIELD_SEP); out.println(p.getPrice()); } return true; } catch (IOException e) { System.out.println(e); return false; } } @Override public boolean add(Product p) { products.add(p); return this.saveAll(); }

@Override public boolean delete(Product p) { products.remove(p); return this.saveAll(); }

@Override public boolean update(Product newProduct) { Product oldProduct = this.get(newProduct.getCode()); int i = products.indexOf(oldProduct); products.remove(i);

products.add(i, newProduct);

return this.saveAll(); } }