Why doesnt it work?

Frage zur Aufgabe

Noch ein Adapter

Java Core, Level 9, Lektion 3

In der Diskussion

the validation isnt very helpfull in finding the error...

Adaptiere Scanner an das PersonScanner-Interface.
Die Adapterklasse ist PersonScannerAdapter.
Erstelle in der Adapterklasse ein privates Scanner-Feld namens fileScanner.
Initialisiere das Feld in einem Konstruktor mit einem Scanner-Parameter.

Die Datei speichert Daten im folgenden Format:
John Michael Peterson 12 31 1950
Larry Thomas Gates 12 31 1957

Die Datei enthält Informationen über zahlreiche Personen. Jede Zeile enthält Daten für eine einzelne Person. Die read()-Methode darf nur die Informationen einer Person lesen.

Anforderungen:

PersonScanner muss ein Interface sein.
Die Klasse PersonScannerAdapter muss das PersonScanner-Interface implementieren.
Die Klasse PersonScannerAdapter muss ein privates Scanner-Feld namens fileScanner besitzen.
Die Klasse PersonScannerAdapter muss einen Konstruktor mit einem Scanner-Parameter besitzen.
Die close()-Methode der PersonScannerAdapter-Klasse muss den Aufruf an fileScanner delegieren.
Die read()-Methode der PersonScannerAdapter-Klasse muss eine Zeile aus der Datei lesen, sie parsen und nur die Daten einer Person als ein Person-Objekt zurückgeben.

package de.codegym.task.task19.task1904; import java.io.IOException; import java.sql.Date; import java.util.Scanner; /* Noch ein Adapter */ public class Solution { public static void main(String[] args) { } public static class PersonScannerAdapter implements PersonScanner { private Scanner fileScanner; public PersonScannerAdapter(Scanner scanner){ this.fileScanner = scanner; } @Override public void close() throws IOException { fileScanner.close(); } public Person read(){ String tanga = fileScanner.nextLine(); String[] array = tanga.split(" ",4); Person ergebnis = new Person(array[0],array[1],array[2], Date.valueOf(array[3])); return ergebnis; } } }

Kommentare (4)

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Lisa

Level 41

27 September 2021, 11:01

Did you test your code? I expect that it won't work cause of Date.valueOf valueOf(String s) Converts a string in JDBC date escape format to a Date value. JDBC date escape format syntax: 'yyyy-mm-dd'.. but that's not what you feed it, no, no, no... no tasty food for valueOf 🤢 Just write test code for your main method like:

PersonScannerAdapter psa = new PersonScannerAdapter(new Scanner(new File("path_to_your_test_file")));
System.out.println(psa.read());
psa.close();

copy the given sample data in a file and see what happens (main needs of course a throws IOException or try/ catch)... yeah, yeah, I'd love to see that 😜🤪 but I bet it throws some sort of Exception... maybe IllegalArgumentException, crazy, crazy 🤪😜 spoiler spoiler spoiler those line would create an output valueOf accepts (you also can see the problem working with the different Date classes)

String line = "Larry Thomas Gates 12 31 1957";
java.util.Date d = java.sql.Date.valueOf(line.replaceFirst(".* (\\d{2}) (\\d{2}) (\\d{4})$", "$3-$1-$2"));

Guadalupe Gagnon

Level 37 , Tampa, United States

27 September 2021, 13:52

Everything Lisa said is correct and great information. I have one thing to add. Typically I start out by sub testing bits and pieces of my code before creating a file to fully test the functionality. In this code, I would assume the Scanner is working properly and test that the rest of the algorithm works. This would be the splitting of the file into the 3 names and 1 date, then the conversion of the date in String format to Date format. In which case this simple bit of code would show where the problem was occurring:

String[] x = "John Michael Peterson 12 31 1950".split(" ", 4);
System.out.println(Arrays.toString(x));
System.out.println(java.sql.Date.valueOf(x[3]));

When running this an IllegalArgumentException is thrown on line 3 in which case I would search google, most likely the Java docs, for why the exception is occurring. It would be occurring for the reason that Lisa said, the String is not formatted properly.

FreshF_INDAHOOD

Level 23 , Augsburg, Germany

27 September 2021, 15:10

public Person read() throws ParseException {

           String tanga = fileScanner.nextLine();
           String[] array = tanga.split(" ",4);
           Date date =  new SimpleDateFormat("MM dd yyyy").parse(array[3]);


           Person ergebnis = new Person(array[2],array[0],array[1], date);
           return ergebnis;
       }

this is how I made it work. I had to change the order of the names, since the order you read is different from the order the constructor needs it. and I used this SimpleDateFormat to get the date going. Tanks for the hint with the date, i had to much trust in the valueOf(). Knowing that the date is the problem was quite helpful in working on that ugly Code😂🤪 Thanks a lot guys and @Lisa, I am very sorry if u had to vomit while reading my Code🤪🤪🤪🤪

Lisa

Level 41

27 September 2021, 16:40

Oh no.... it is not me who has a sensitive stomach, valueOf is. This time your code is pretty OK. You just ended up in the wrong class. Using split seems to be the default approach here. replaceFirst and the regex even may have worked together with your valueOf try (nearly out of the box). Thumbs up, my fellow coder, yeah, yeah 😜🤪... we'll become more, more