Where Is The Exception?

Question about the task

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The validation says I need to check the exceptions in the save/load methods, but I don't see any? Can anyone help me figure out where the exceptions are coming from?

Implement the logic for file IO for the CodeGym class.
The file your_file_name.tmp can contain several CodeGym objects.
The main method exists just for you and is not involved in testing the solution.

Requirements:

The read/write logic in the save/load methods must work correctly when the users list is empty.
The read/write logic in the save/load methods must work correctly when the users list is not empty.
The Solution.CodeGym class should not support the Serializable interface.
The Solution.CodeGym class must be public.
The Solution.CodeGym class should not support the Externalizable interface.

package com.codegym.task.task20.task2002; import java.io.*; import java.util.ArrayList; import java.util.List; import java.util.Date; import java.util.Scanner; /* Reading and writing to a file: CodeGym */ public class Solution { public static void main(String[] args) { // You can find your_file_name.tmp in your TMP directory or adjust outputStream/inputStream according to your file's actual location try { File yourFile = File.createTempFile("your_file_name", null); OutputStream outputStream = new FileOutputStream(yourFile); InputStream inputStream = new FileInputStream(yourFile); CodeGym codeGym = new CodeGym(); // Initialize users field for the codeGym object here codeGym.save(outputStream); outputStream.flush(); CodeGym loadedObject = new CodeGym(); loadedObject.load(inputStream); // Here check that the codeGym object is equal to the loadedObject object outputStream.close(); inputStream.close(); } catch (IOException e) { //e.printStackTrace(); System.out.println("Oops, something is wrong with my file"); } catch (Exception e) { //e.printStackTrace(); System.out.println("Oops, something is wrong with the save/load method"); } } public static class CodeGym { public List<User> users = new ArrayList<>(); public void save(OutputStream outputStream) throws Exception { // Implement this method PrintWriter writer = new PrintWriter(outputStream); String isUsersPresent = users.size() > 0 ? "Yes" : "No"; writer.println(isUsersPresent); writer.flush(); if (isUsersPresent.equals("Yes")) { writer.println(users.size()); writer.flush(); for(User user : users){ boolean hasFirstName = user.getFirstName() != null; writer.println(String.valueOf(hasFirstName)); writer.flush(); if(hasFirstName){ writer.println(user.getFirstName()); writer.flush(); } boolean hasLastName = user.getLastName() != null; writer.println(hasLastName); writer.flush(); if(hasLastName){ writer.println(user.getLastName()); writer.flush(); } boolean hasBirthDate = user.getBirthDate() != null; writer.println(hasBirthDate); writer.flush(); if(hasBirthDate){ writer.println(user.getBirthDate().getTime()); writer.flush(); } //default for boolean is false: this will always have a value. writer.println(user.isMale()); writer.flush(); boolean hasCountry = user.getCountry() != null; writer.println(hasCountry); writer.flush(); if(hasCountry){ writer.println(user.getCountry().getDisplayName()); writer.flush(); } } writer.println(); } writer.close(); } public void load(InputStream inputStream) throws Exception { // Implement this method Scanner reader = new Scanner(inputStream); if(users.isEmpty()){ String isUsersPresent = reader.nextLine(); if(isUsersPresent.equals("Yes")){ for(int i = 0; i < Integer.parseInt(reader.nextLine()); i++){ User newUser = new User(); //check if firstName exists or not if(reader.nextLine().equals("true")){ //set First Name newUser.setFirstName(reader.nextLine()); } //check if lastName exists or not if(reader.nextLine().equals("true")){ //set Last Name newUser.setLastName(reader.nextLine()); } //check if BirthDate exists or not if(reader.nextLine().equals("true")){ //set Birth Date newUser.setBirthDate(new Date(Long.parseLong(reader.nextLine()))); } //set the IsMale variable String isMale = reader.nextLine(); if(isMale.equals("true")){ newUser.setMale(true); } else{ newUser.setMale(false); } //check if Country exists or not if(reader.nextLine().equals("true")){ //set Country newUser.setCountry(User.Country.valueOf(reader.nextLine())); } users.add(newUser); } reader.close(); } } } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; CodeGym codeGym = (CodeGym) o; return users != null ? users.equals(codeGym.users) : codeGym.users == null; } @Override public int hashCode() { return users != null ? users.hashCode() : 0; } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

22 January 2020, 18:24

solution

The problem is with writing and reading to set the country. In the save method you write to the file the display name of the country, which for "UNITED_STATES" is "United States". Then in the read method you use Country.valueOf() to set the country. The problem is that this method works with the actual value "UNITED_STATES" and won't work for the display name "United States". This is why an exception is being thrown.

Guadalupe Gagnon

Level 37 , Tampa, United States

22 January 2020, 18:59

useful

I would recommend simplifying your code a bit. If you think about it a little, you do not need to write "true", "false", "yes", "no", and the amount of users present to the file. In the save method, a simple loop would only write to the file if users are present. In the load loop, if nothing is written then there are no users. This would completely negate the "yes", "no", and size of the users array being printed to the file, lines 48-53. You could write all the user data in a string, separated by some random character like this: "firstName~lastName~birthDate~isMale~country" then output that line directly to the file using the outputStream. So the code for all this would look something like this:

public void save(OutputStream outputStream) throws Exception {
      for(int i = 0; i < users.size(); i++){
         String user = /*code to build the user line*/;
         outputStream.write(user.getBytes());
         outputStream.write(10); // new line char
      }
   }
}

Then in the load method you could read each line in and split the data by the random character, so that the line's array would be: ["firstname", "lastname", "birthDate", "isMale", "country"] then create a new user and add it to the users list. The code would look like this:

public void load(InputStream inputStream) throws Exception {
   BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
   String line;
   while((line = reader.readLine()) != null){
      if(line.equals("")) return;
      String[] data = line.split("~");
      User newUser = new User();
      /* code to fill newUser's information*/
      users.add(newUser);
   }
}

You don't need to test if the User's fields have values. You can save the default values if they haven't been changed and use them when loading.