Append to File & Read from File, but nothing happens

Misanthrope3011 :

I am trying to write a program that creates a kind of database in a file. Its base functions are Read all records and Append a new record to file, but every time I try to append something nothing happens.

Here is my code:

public class SavingInFile {
    FileWriter example=new FileWriter("template.txt",true);
    FileReader example2=new FileReader("template.txt");
    BufferedWriter setNewRecord=new BufferedWriter(example);
    BufferedReader readTheRecords=new BufferedReader(example2);

    public SavingInFile() throws IOException {
    }

    void safeNewData(PersonRecord anotherPersonRecord) throws IOException {
        setNewRecord=new BufferedWriter(example);
        setNewRecord.append(anotherPersonRecord.addNewRecord());

    }

     ArrayList<PersonRecord> getDataFromFile() throws IOException {
        setNewRecord=new BufferedWriter(example);

        readTheRecords=new BufferedReader(example2);
         ArrayList<PersonRecord> valuesKeeper = new ArrayList<>();


         System.out.println(readTheRecords.readLine());

        while(readTheRecords.readLine()!=null) {
            if(readTheRecords.readLine()!=null) {
                String[] tempArray = readTheRecords.readLine().split(";");
                PersonRecord tempRecord = new PersonRecord();
                tempRecord.name = tempArray[0];
                tempRecord.age = Integer.parseInt(tempArray[1]);
                tempRecord.surname = tempArray[2];
                tempRecord.salary = Integer.parseInt(tempArray[3]);
            }
        }

        this.setNewRecord.close();
        return valuesKeeper;
    }

    public void displayArrayList() throws IOException {
        ArrayList<PersonRecord> example=this.getDataFromFile();
        Iterator<PersonRecord> iterateValues=example.iterator();

        while(iterateValues.hasNext()) {
            System.out.println(iterateValues.next().name+ " "+iterateValues.next().surname+ " "+iterateValues.next().age+ "  " + iterateValues.next().salary+ " ");
        }
    }

    public void closeBuffers() throws IOException {
        this.readTheRecords.close();
    }
}

This is a Person Class, which contains dataFields

public class PersonRecord {
    int age;
    double salary;
    String name;
    String surname;

    public PersonRecord() {
    }

    public PersonRecord(int age, double salary, String name, String surname) {
        this.age = age;
        this.salary = salary;
        this.name = name;
        this.surname = surname;
    }

    public int getAge() {
        return age;
    }

    public double getSalary() {
        return salary;
    }

    public String getName() {
        return name;
    }

    public String getSurname() {
        return surname;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setSurname(String surname) {
        this.surname = surname;
    }

    String addNewRecord() {
        return this.name+";"+this.surname+";"+String.valueOf(this.age)+";"+String.valueOf(this.salary);
    }
}

and here is my main:

public class Main {

    public static void main(String[] args) throws IOException {
        SavingInFile bufferToFile = new SavingInFile();
        ArrayList<PersonRecord> keepRecords=bufferToFile.getDataFromFile();

        PersonRecord x = new PersonRecord(10,13,"34","45");

        bufferToFile.saveNewData(x);
        ArrayList<PersonRecord> example=bufferToFile.getDataFromFile();
        bufferToFile.displayArrayList();
        bufferToFile.closeBuffers();
    }
}

Any suggestions about what is wrong there?

nazar_art :

Your code has a lot of "bad smells" places. Just go through following resources:

• Type List vs type ArrayList in Java
• Reading file in Java
• Java – Try with Resources
• you shadowed some parameters at your method and didn't close it correctly after using
• formatting your code help a lot (exactly before posting it like a question)
• meaningfully named for variables help reading and to maintain code

So following is the rewritten solution

Record class:

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
class PersonRecord {
    String name;
    String surname;
    int age;
    double salary;

    String addNewRecord() {
        return String.format("%s;%s;%s;%s\n", this.name, this.surname, this.age, this.salary);
    }
}

Turn separate utility class for processing operation with file for persons:

final class PersonOperations {

    public static void appendToFile(String fileName, List<PersonRecord> persons) throws IOException {
        @Cleanup
        BufferedWriter buffWriter = new BufferedWriter(new FileWriter(fileName, true));

        for (PersonRecord person : persons) {
            buffWriter.append(person.addNewRecord());
        }
    }

    public static List<PersonRecord> readFile(String fileName) throws IOException {
        @Cleanup
        BufferedReader buffReader = new BufferedReader(new FileReader(fileName));
        List<PersonRecord> persons = buffReader.lines()
                .filter(Objects::nonNull)
                .map(str -> {
                    String[] temp = str.split(";");
                    return PersonRecord.builder()
                            .name(temp[0])
                            .surname(temp[1])
                            .age(Integer.parseInt(temp[2]))
                            .salary(Double.parseDouble(temp[3]))
                            .build();
                })
                .collect(Collectors.toList());
        System.out.println("persons from file: " + persons);
        return persons;
    }

    public static void displayPersons(List<PersonRecord> persons) {
        for (PersonRecord person : persons) {
            System.out.println(person);
        }
    }
}

Final demo code will look like:

public class FileDemo {
    public static void main(String[] args) throws IOException {
        String fileName = "template.txt";

        List<PersonRecord> records = PersonOperations.readFile(fileName);
        PersonOperations.displayPersons(records);

        PersonRecord personRecord = new PersonRecord("Bob", "Dilan", 34, 4500);
        PersonOperations.appendToFile(fileName, List.of(personRecord));

        List<PersonRecord> persons = PersonOperations.readFile(fileName);
        PersonOperations.displayPersons(persons);
    }
}

Also, if we don't need any operation with a result from the file, we could add static import and write:

displayPersons(readFile(fileName)); 

Console output:

persons from file: [PersonRecord(name=Garry, surname=Ford, age=45, salary=6000.0)]
PersonRecord(name=Garry, surname=Ford, age=45, salary=6000.0)
persons from file: [PersonRecord(name=Garry, surname=Ford, age=45, salary=6000.0), PersonRecord(name=Bob, surname=Dilan, age=34, salary=4500.0)]
PersonRecord(name=Garry, surname=Ford, age=45, salary=6000.0)
PersonRecord(name=Bob, surname=Dilan, age=34, salary=4500.0)

template.txt file before execution:

Garry;Ford;45;6000  

template.txt after execution:

Garry;Ford;45;6000 
Bob;Dilan;34;4500.0

Also, I used Lombok framework annotations there. You can keep native getters and setters as well. And closing resources after reading it (with Autocloseable or with finally block).

As alternatives for saving to txt file you could consider:

• Serialisation: Java Serialisation
• Serialisation to the XML file.