CodeGym/Help with Java Tasks/Is it just me or is this another time CodeGym didn't teac...

Level 26

Rancho Cucamonga

28.10.2019
1785views
13comments

Is it just me or is this another time CodeGym didn't teach us a damn thing about the skills we will need to do the tasks at hand. Great Start to Section 20...

Question about the task

Under discussion

Does anyone have any links or documentation that is actually useful for completing these tasks. I tried combing the questions section and didn't find anything and then I tried to just read and write some code I found in the same places hoping to get some understanding but that did not work out at all. I'm getting fed up with the lack of actual teaching this site does while throwing all kinds of tasks with requirements they didn't cover and the worst part is is that is still the best thing for learning to code I have come across on the web. Please, someone set me strait if I am wrong. Thanks in advance! If I was keen to looking everything up to do a task as hand without help or guidance then why wouldn't I just use Codingame for free because that is all that seems to happen on this site as of late.

Implement the logic for file IO for the Human class.
The Human class's name field can't be empty.
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 assets list is empty.
The read/write logic in the save/load methods must work correctly when the name field and assets list are not empty.
The Solution.Human class should not support the Serializable interface.
The Solution.Human class must be public.
The Solution.Human class should not support the Externalizable interface.

package com.codegym.task.task20.task2001; import java.io.*; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.Scanner; /* Reading and writing to a file: Human */ public class Solution { public static void main(String[] args) { // Update the string passed to the createTempFile method based on the path to a file on your hard drive try { File yourFile = File.createTempFile("your_file_name", null); OutputStream outputStream = new FileOutputStream(yourFile); InputStream inputStream = new FileInputStream(yourFile); Human smith = new Human("Smith", new Asset("home", 999_999.99), new Asset("car", 2999.99)); smith.save(outputStream); outputStream.flush(); Human somePerson = new Human(); somePerson.load(inputStream); inputStream.close(); // Check that smith is equal to somePerson } 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 Human { public String name; public List<Asset> assets = new ArrayList<>(); public Human() { } public Human(String name, Asset... assets) { this.name = name; if (assets != null) { this.assets.addAll(Arrays.asList(assets)); } } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Human human = (Human) o; if (name != null ? !name.equals(human.name) : human.name != null) return false; return assets != null ? assets.equals(human.assets) : human.assets == null; } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; result = 31 * result + (assets != null ? assets.hashCode() : 0); return result; } public void save(OutputStream outputStream) throws Exception { PrintWriter writer = new PrintWriter(outputStream); String isHumanPresent = name != null ? "yes" : "no"; writer.println(isHumanPresent); ; if (name != null) { for (Asset a : assets) { writer.println(a.getName()); writer.println(a.getPrice()); } } writer.flush(); writer.close(); } public void load(InputStream inputStream) throws Exception { Scanner scanner = new Scanner(inputStream); name = scanner.nextLine(); String isAssetPresent = scanner.nextLine(); if (isAssetPresent.equals("yes")) { while (scanner.hasNext()) { Asset asset = new Asset(scanner.nextLine(), Double.parseDouble(scanner.nextLine())); assets.add(asset); } scanner.close(); } } } }

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Fabian Andiel

Level 25 , Vienna, Austria

17 September 2020, 10:01

With this example it is important not wanting to understand everything.!!! It appears to be overwhelming but it is important to do in order to get a better grasp. When you need help just look at the other responses. And ignore the condescending comments of the hungarian person.

Csaba Gódor

Level 36 , Budapest, Hungary

14 January 2020, 12:30

first attempt, no issue, easypeasy, sry...

public void save(OutputStream outputStream) throws Exception {
           try (
                   PrintWriter writer = new PrintWriter(outputStream);
           ) {
               writer.println(this.name);
               for (Asset asset : assets) {
                   writer.println(asset.getName());
                   writer.println(asset.getPrice());
               }
           }
       }

       public void load(InputStream inputStream) throws Exception {
           try(
           BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
           ) {
               this.name = bufferedReader.readLine();
               while (bufferedReader.ready()) {
                   this.assets.add(new Asset(bufferedReader.readLine(), Double.parseDouble(bufferedReader.readLine())));
               }
           }
       }

Hossein Shams

Level 1 , Atlanta, United States

29 October 2019, 23:57

And about the task, I think the logic of your code is fine. I'm not sure if the validation system tests a certain way of coding or just the outcome of it. The only missing part I can see in your code, is that the code won't write the instant's name in the file. That can be the issue. Here is my version of Save and Load methods. I hope they'll be useful.

public void save(OutputStream outputStream) throws Exception {
    // Implement this method
    outputStream.write(name.getBytes());
    for (Asset asset : assets) {
        outputStream.write(64); // @ character, separates assets
        outputStream.write(asset.getName().getBytes());
        outputStream.write(126); // ~ character, separates asset name and value
        outputStream.write(String.valueOf(asset.getPrice()).getBytes());
    }
}

public void load(InputStream inputStream) throws Exception {
    // Implement this method
    StringBuilder wholeFile = new StringBuilder();
    while (inputStream.available() > 0){
        wholeFile.append((char) inputStream.read());
    }
    System.out.println(wholeFile.toString());
    String[] brokenLine = wholeFile.toString().split("@");
    name = brokenLine[0];
    for (int i = 1; i < brokenLine.length; i++){
        String[] oneAsset = brokenLine[i].split("~");
        assets.add(new Asset(oneAsset[0],Double.parseDouble(oneAsset[1])));
    }
}

Guadalupe Gagnon

Level 37 , Tampa, United States

30 October 2019, 18:51

This is how I solved it, but I just like to suggest that reading/writing to a file is a lot cleaner and WAAAAY more efficient if done once instead of a bunch of times. See code below with modifications:

public void save(OutputStream outputStream) throws Exception {
        StringBuilder sb = new StringBuilder();
        sb.append(name);
        for (Asset asset : assets) {
            sb.append("@");
            sb.append(asset.getName().getBytes());
            sb.append("~");
            sb.append(asset.getPrice());
        }
        outputStream.write(sb.toString().getBytes());
    }

    public void load(InputStream inputStream) throws Exception {
        byte[] bytes = new byte[inputStream.available()];
        inputStream.read(bytes);
        String wholeFile = new String(bytes);

        String[] brokenLine = wholeFile.split("@");
        name = brokenLine[0];
        for (int i = 1; i < brokenLine.length; i++){
            String[] oneAsset = brokenLine[i].split("~");
            assets.add(new Asset(oneAsset[0],Double.parseDouble(oneAsset[1])));
        }
    }

Hossein Shams

Level 1 , Atlanta, United States

1 November 2019, 13:34

Thank you Guadalupe. You are always a big help. Actually, I didn't know we can use input/ouput streams like this: (outputStream.write(sb.toString().getBytes()); inputStream.read(bytes);) Writing the whole file at once definitely makes storage and retrieving data much faster when you working with HardDrives, I'm not sure about the new Random Access Memories like flash drives and SSDs. Thank you for your information Mr. Developer

Guadalupe Gagnon

Level 37 , Tampa, United States

1 November 2019, 13:55

The time saved this way is staggering. I have a NVME m.2 SSD on my computer. Take a look at this program that I just wrote that tests reading one byte at a time vs. reading all at once:

public class Solution {
    public static void main(String[] args) throws IOException {
        String fileName = "C:\\Users\\lupeh\\Desktop\\temp\\Original.txt";
        System.out.println("Creating FileInputStream to read one byte at a time");
        long start = System.currentTimeMillis();
        try(FileInputStream test1 = new FileInputStream(fileName)){
            System.out.println("\tFile size: " + test1.available());
            System.out.println("\tStarting read");
            while(test1.available() > 0) test1.read();
        }
        long end = System.currentTimeMillis();
        System.out.println("\tRead complete. Time taken: " + (end-start));
        System.out.println("Creating FileInputStream to read all byte in one read");
        start = System.currentTimeMillis();
        try(FileInputStream test1 = new FileInputStream(fileName)){
            int size = test1.available();
            byte[] data = new byte[size];
            System.out.println("\tFile size: " + size);
            System.out.println("\tStarting read");
            test1.read(data);
        }
        end = System.currentTimeMillis();
        System.out.println("\tRead complete. Time taken: " + (end-start));

    }
}

The output on my computer is: Creating FileInputStream to read one byte at a time File size: 158047 Starting read Read complete. Time taken: 1379 Creating FileInputStream to read all byte in one read File size: 158047 Starting read Read complete. Time taken: 1 Same file took 1379 milliseconds to read one byte at a time (and not stored). Reading all at once and storing took 1 millisecond.

Hossein Shams

Level 1 , Atlanta, United States

2 November 2019, 16:48

That's a piece of good information to have in mind while designing a file accessed program. There might be a slowdown in accessing OS's file API too, I guess. Anyway, thank you again for being so caring and serious in helping others with their programming problems.

yehuda b

Level 23 , Beersheba, Israel

21 November 2020, 23:29

first of all thank you for answering here, as otherwise I never would have finished this task, it took me a while to realize that the hashcode and equal methods, have nothing to do with the user (maybe I'm dumb, and prob. that's the reason it passed with my filepath, in the create tempfile method). Also, in your code it doesn't check for isHumanPresent, I assume it's intentional as it isn't relevant to the question?

Hossein Shams

Level 1 , Atlanta, United States

29 October 2019, 23:54

I agree with most of your statement up there. I think CodeGym is trying to put us in real life situations, where you've been assigned a task with no clue what the client or your co-worker or manager really needed. Just some nonsense commandments. Hang in there bro, you'll be a great programmer.

Jason

Level 26 , Rancho Cucamonga, United States

30 October 2019, 18:16

Thanks, and you're probably right. I only seem to get upset about it when I can't figure it out., but It's just sometimes I just want to learn and I just want to be able to absorb gobs of information and then know that information actually applies to the task at hand

Johannes

Level 27 , Centurion, Pretoria, South-Africa

21 April 2020, 09:35

I know the feeling.

Royal Summers

Level 2 , Warrenville, United States

29 October 2019, 01:40

Here's an assignment that I recently completed that appears similar: package com.RoyalSummers.L06PracticeHandsOn; import java.io.BufferedReader; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; public class FileInputOutput { public static void main(String[] args) { // array of songs String songs[] = {"Rock with You", "Sooth Criminal", "Wanna be Startin Something","Thriller", "Beat It"}; // make array an String using StringBuilder StringBuilder sb = new StringBuilder(); for(String jackson : songs ) { sb.append(jackson).append(", "); } // write songs array into file. Use try/catch to return any exception errors try { FileWriter writer = new FileWriter("/Users/Royal and Carla/Desktop/songs.txt"); writer.write(sb.toString()); writer.close(); } catch(Exception e) { System.out.println("Error when writing songs.txt."); } // read contents of the file. Use try/catch to return any exception errors try { BufferedReader reader = new BufferedReader(new FileReader("/Users/Royal and Carla/Desktop/songs.txt")); String line; while((line = reader.readLine()) != null) { System.out.println(line); } reader.close(); } catch(Exception e) { System.out.println("Error when reading songs.txt."); } } } Hope this helps...

Jason

Level 26 , Rancho Cucamonga, United States

29 October 2019, 05:52

I'm sorry Royal Summers but I don't see how that helps me at all.