Why is exception occurring ?

Question about the task

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Going mad here cant find what is problem. I am getting this from hint : "Check why an exception occurs in the save/load methods."

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.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.List; /* 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); if (!users.isEmpty()) { for (User u : users) { writer.println(u.getFirstName()); writer.println(u.getLastName()); writer.println(u.getBirthDate().toString()); writer.println(u.isMale()); writer.println(u.getCountry().getDisplayName()); } writer.flush(); } } public void load(InputStream inputStream) throws Exception { // Implement this method BufferedReader reader = new BufferedReader(new InputStreamReader( inputStream)); while (reader.ready()) { User newUser = new User(); newUser.setFirstName(reader.readLine()); newUser.setLastName(reader.readLine()); SimpleDateFormat dateFormat = new SimpleDateFormat("dd MM yyyy"); Date d = dateFormat.parse(reader.readLine()); newUser.setBirthDate(d); newUser.setMale(Boolean.parseBoolean(reader.readLine())); String country = reader.readLine(); switch (country) { case "United States": newUser.setCountry(User.Country.UNITED_STATES); case "United Kingdom": newUser.setCountry(User.Country.UNITED_KINGDOM); case "Other": newUser.setCountry(User.Country.OTHER); } users.add(newUser); } } @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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Goran

Level 41 , Belgrade, Serbia

11 October 2020, 10:09

Thank you dhanush and Guadalupe Gagnon ! I fixed for time reading from dhanush. And added break to switch method like Guadalupe Gagnon suggested!

Guadalupe Gagnon

Level 37 , Tampa, United States

7 October 2020, 15:11

useful

#1 you need to test the code to ensure that it is working. change line 17 of the Solution class to be a String and a path to a file on your computer then copy and paste this over lines 22-28 with something like this that adds Users to the users arraylist:

// Initialize users field for the codeGym object here
User temp1 = new User();
temp1.setBirthDate(new Date());
temp1.setFirstName("Guadalupe");
temp1.setLastName("Gagnon");
temp1.setMale(true);
temp1.setCountry(User.Country.UNITED_STATES);

User temp2 = new User();
temp2.setBirthDate(new Date());
temp2.setFirstName("Someone");
temp2.setLastName("else");
temp2.setMale(false);
temp2.setCountry(User.Country.UNITED_KINGDOM);

codeGym.users.add(temp1);
codeGym.users.add(temp2);


// CHECK THE OUTPUT IN THE FILE
codeGym.save(outputStream);
outputStream.flush();


CodeGym loadedObject = new CodeGym();
loadedObject.load(inputStream);
System.out.println("Original users:");
System.out.println(codeGym.users);

System.out.println("Loaded users:");
System.out.println(loadedObject.users);

and then add a toString() method to the Users class:

@Override
public String toString() {
   return "User{" +
      "firstName='" + firstName + '\'' +
      ", lastName='" + lastName + '\'' +
      ", birthDate=" + birthDate +
      ", isMale=" + isMale +
      ", country=" + country +
      '}';
}

Now you can run the code and check the results. I am getting an error in the load method which is caused because the data being read in does not match what the code expects. I would recommend looking at the data in the file saved on your computer to see what is being output so that you can match the load method to expect the EXACT format. Also, switch cases to break after each.

dhanush

Level 30 , Chennai, India

7 October 2020, 06:04

useful

In the line 56 try by doing like this

writer.println(u.getBirthDate().getTime());

and also for setting the birthday try to parse a long in the date constructor it will be a single line code like,

newUser.setBirthDate(new Date(Long.parseLong(reader.readLine())));

because you are converting the date format to String,then it will print in String(Date connot be converted into String) so it throws an exception.

Goran

Level 41 , Belgrade, Serbia

7 October 2020, 12:14

I did try that but still problem with requirement 2 :/ If that first problem maybe something else is wrong then, but don't know what :/

dhanush

Level 30 , Chennai, India

7 October 2020, 13:57

Actually your'e Deserialization is not done correctly because of setCountry donno where the problem is try a different way and the main thing is if you serialize and deserialize means both should be same but in your case it's not until i tested your code. Look at the output of the given Screenshot. and try to do in another way like

newUser.add(user.Country.valueOf(reader.readLine()));

and also line 59 remove the getDisplayName(). Now it's fine i think so.