Question

My problem is that I have to write code to check if a customers name is already in my txt file (Customers.txt).

The problem is that I check with hashset if the customer is in the file and he says that he isn’t in the file while he is.(Checked it manually)
Please help me solve this.

The code that I already have is below.

    public class Customer {
    //declaration
    public static String S;
    private String line ;
    public String nameCustomer;


/**
 * constructor
 */
public Klant(){}

/**Checking of the customer is in the file
 */
public void getCustomer() {
    // make SimpleInOutDialog      
        SimpleInOutDialog  input = new SimpleInOutDialog("Customers");
        nameCustomer = input.readString("Give in the name");
    try{
    BufferedReader br = new BufferedReader(new FileReader("L:\\Documents/Informatica/6de jaar/GIP/Customers.txt"));
    HashSet<String> hs = new HashSet<String>();
    int i = 0;
    while ((line = br.readLine()) != null)
    {
        i++;
        if (i == 1){hs.add(br.readLine());}

        if (i % 4 == 0){hs.add(br.readLine());}

    }
    if(hs.contains(nameCustomer)){
        //the customer exists
     input.showString("The customer exists", "");
     }else{input.showString("The customer does not exist, we will make a new one", "");
         setNieuweKlant();}


    }catch (Exception e){//Catch when there are errors
        System.err.println("Error: " + e.getMessage());}

}


/**
 * make a new customer
 */

public void Make new customer(){
    // make SimpleInOutDialog     
    SimpleInOutDialog  input = new SimpleInOutDialog("A new customer");
    //input
    S = "Name customer: " + input.readString("Give in your name:");
WriteToFile();
S = "Adress: " + input.readString("Give your adress");
WriteToFile();
S = "Telephonenummber: " + input.readString("Give your telephonenumber");
WriteToFile();
//making a customerID
  UUID idCustomer = UUID.randomUUID();  
S = "CustomerID: " + customerID.toString();
WriteToFile();

}


/**
 * Schrijft de gegevens weg naar het bestand
 */


 public void WriteToFile(){
try{

FileWriter writer = new FileWriter("L:\\Documents/Informatica/6de jaar/GIP/Customer.txt", true);
BufferedWriter out = new BufferedWriter(writer);
//Wrting away your data
out.write(S);

//Closing the writer
out.close();


}catch (Exception e){//Catch when there are errors
    System.err.println("Error: " + e.getMessage());
    }
    }

Dutcht Code

public class Klant {
    //declaratie van de variabele die de tekst voorsteld
    public static String S;
    private String line ;
    public String naamklant;


/**
 * constructor
 */
public Klant(){}

/**Controleerd of de klant al bestaat
 */
public void getKlant() {
    // SimpleInOutDialog aanmaken     
        SimpleInOutDialog  input = new SimpleInOutDialog("Klanten");
        naamklant = input.readString("Geef de volledige naam in");
    try{
    BufferedReader br = new BufferedReader(new FileReader("L:\\Documents/Informatica/6de jaar/GIP/Klanten.txt"));
    HashSet<String> hs = new HashSet<String>();
    int i = 0;
    while ((line = br.readLine()) != null)
    {
        i++;
        if (i == 1){hs.add(br.readLine());}

        if (i % 4 == 0){hs.add(br.readLine());}

    }
    if(hs.contains(naamklant)){
        //klant bestaat
     input.showString("De klant bestaat", "");
     }else{input.showString("De klant bestaat niet, er wordt een nieuwe klant aangemaakt", "");
         setNieuweKlant();}


    }catch (Exception e){//Catch wanneer er errors zijn
        System.err.println("Error: " + e.getMessage());}

}


/**
 * Maakt een nieuwe klant aan 
 */

public void setNieuweKlant(){
    // SimpleInOutDialog aanmaken     
    SimpleInOutDialog  input = new SimpleInOutDialog("Een nieuwe klant");
    //input
    S = input.readString("Geef de volledige naam in");
    WriteToFile();
    S = "Adres: " + input.readString("Geef het adres op");
    WriteToFile();
    S = "Telefoonummer: " + input.readString("Geef het telefoonnummer op");
    WriteToFile();
    //een klantennummer aanmaken 
      UUID idKlant = UUID.randomUUID();  
    S = "Klantnummer: " + idKlant.toString();
    WriteToFile();

}


/**
 * Schrijft de gegevens weg naar het bestand
 */
public void WriteToFile(){

    try{

        FileWriter writer = new FileWriter("L:\\Documents/Informatica/6de jaar/GIP/Klanten.txt", true);
        BufferedWriter out = new BufferedWriter(writer);
        //uw gegevens wegschrijven
        out.write(S);
        out.newLine();
        //de writer sluiten
        out.close();


    }catch (Exception e){//Catch wanneer er errors zijn
        System.err.println("Error: " + e.getMessage());}



    }


}

Answer 1

I’m really not sure what you’re trying to do overall (reading every 4th line, etc.), but I wouldn’t use a HashSet if all you want is to check if a string exists in a file.

Here’s a complete program for checking if a string exists in a file:

import java.io.*;

public class CheckName
{
  private static boolean doesNameExistInFile(String name, String filename)
    throws FileNotFoundException, IOException
  {
    BufferedReader reader = new BufferedReader(new FileReader(filename));

    String line = null;

    try {
      while ((line = reader.readLine()) != null) {
        if (line.equals(name))
          return true;
      }

    } finally {
      // Always close() before exiting.
      reader.close();
    }

    return false;
  }

  public static void main(String[] args)
    throws FileNotFoundException, IOException
  {
    boolean exists = doesNameExistInFile("Bender", "input.txt");

    System.out.println(exists ? "Exists!" : "Does not exist.");
  }
}

Contents of input file input.txt:

Leela
Fry
Professor
Hermes
Zoidberg

A couple of things to note:

1. We don’t read the entire file. We stop reading once we’ve found the string, as that’s all we’re interested in.
2. Always close() before exiting, whether string is found or not. We put the call in the finally block.