Java Parse String in Class Instance

Question

i want parse a String into a Class Instance. My Data come from a .csv.

Code:

@Override
public List<Strasse> getByStadtId(Stadt stadtId){
    return repo.findByStadtId(stadtId);
}

@Override
public void saveStrassenData() {
    StringBuilder builder = new StringBuilder();
    try {
        BufferedReader bufferReader = new BufferedReader(new FileReader("src/main/resources/csv/strassen.csv"));
        while((line = bufferReader.readLine()) != null) {
            String [] data=line.split(",");
            Strasse strasse = new Strasse();
            Stadt stadt = new Stadt();
            strasse.setId(Long.parseLong(data[0]));
            strasse.setName(data[1]);
            strasse.setVerwaltungsKuerzel(data[2]);
            strasse.setStadt(data[3]);
            repo.save(strasse);
        } 
    
    }
    catch (IOException e) {
        //TODO Auto-generated catch block
        e.printStackTrace();
    }
}

In Picture 1 you can see my error.

Picture of the Code

My Class is in the pictures:

The .csv

create a function that parses the string and convert it to the object that you want. Are you passing json as a string? — Panagiotis Bougioukos
– Panagiotis Bougioukos, Commented Jan 4, 2021 at 23:13
You're calling setStadt() which takes an instance of Stadt but you are passing in data[3] which is a String. — Matt
– Matt, Commented Jan 4, 2021 at 23:20

Christian · Accepted Answer · 2021-01-04 23:18:00Z

2

setStadt doesn't take a String. You need to create an instance of Stadt and then you could set it's id.

Something like that:

Stadt stadt = new Stadt();
stadt.setId(data[3]);
strasse.setStadt(stadt);

answered Jan 4, 2021 at 23:18

Christian

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2 Comments

Alex1993 Over a year ago

I get this error -> java.lang.NumberFormatException: For input string: "1"

Alex1993 Over a year ago

Thank you, i found the mistake :) I had a misspelling in the .csv ^^

Joop Eggen · Accepted Answer · 2021-01-05 00:01:23Z

The handling of Stadt and validation of Strasse is missing.

@Override
public void saveStrassenData() {
    Charset charset = StandardCharsets.ISO_8859_1; // Or UTF_8.
    try (InputStream in = getClass().getResourceAsStream("/csv/strassen.csv");
            BufferedReader bufferReader = new BufferedReader(
                new InputStreamReader(in, charset))) {
        while((line = bufferReader.readLine()) != null) {
            String[] data=line.split(",\\s*");
            Strasse straße = new Strasse();

            long stadtId = Long.parseLong(data[3]);
            Stadt stadt = new Stadt(); // repo.getStadtById(stadtId);
            stadt.setId(stadtId);      //

            straße.setId(Long.parseLong(data[0]));
            straße.setName(data[1]);
            straße.setVerwaltungsKuerzel(data[2]);
            straße.setStadt(stadt;     // <--
            repo.save(straße);
        } 
    
    }
    catch (IOException e) { // Better method with throws IOException.
        e.printStackTrace(); // Log.
    }
}

Also the old utility class FileReader uses the default charset, for a German Windows Cp-1252, a superset of ISO-8859-1. For a server likely UTF-8. Better state the charset explicitly, especially when you provide it yourself as read-only resource.

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