Having problem when i sort out data from hashmap. Variables are mixing!

[Tor Ludgivsen]

Hello! Im having a problem with my library system.

the p.name and p.isbn are mixing up.

class UtlanInnlesning {  
    HashMap<String,Person> personm = new HashMap<String,Person>();  
    UtlanInnlesning() {  
        try {  
            Scanner scanner = new Scanner(new FileReader("lan.txt"));  
            while (scanner.hasNextLine()) {  
                //ISBN;DATO;MOBILNR;NAVN;  
                String[] col = scanner.nextLine().split(";");  
                String isbn = col[0];  
                String dato = col[1];  
                String nr = col[2];  
                String name = col[3];  
                personm.put(nr, new Person(nr,isbn,dato,name));  
                  
            }scanner.close();  
        }  
        catch (Exception e) {  
            System.out.println("Error: "+e.getMessage());  
        }  
    }  
      
    void meny() {  
        System.out.println("      ### Utlån ###");    
        System.out.println("(1) Oversikt over lånetagere");  
        System.out.println("(2) Oversikt over utlånte bøker");  
        System.out.println("(3) Hovedmeny");  
        System.out.println("(10) Avslutt");  
        menyValg();  
    }  
      
    void menyValg() {  
        Scanner sc = new Scanner(System.in);  
        String input = sc.next();  
        M m = new M();  
        try {  
            int x = Integer.parseInt(input);  
            System.out.println(x);  
            switch (x) {  
            case 1 : oversikt(); meny(); break;  
            case 2 : meny(); break;  
            case 3 : m.meny(); break;  
            case 10 : break ;  
            default :  
                System.out.println();  
                System.out.println("Error: Velg et tall 1-3 eller 10!");  
                meny();  
            }  
        }  
        catch(NumberFormatException nFE) {                
            System.out.println();  
            System.out.println("Error: Ikke et tall!");  
            meny();  
        }  
        sc.close();  
    }  
      
    //and this is the method that is making all the trouble  
    void oversikt() {         
        Iterator<Person> itt = personm.values().iterator();  
        int a = personm.size();  
        System.out.println("Antall utlånte bøker: "+a);  
        String[] sort = new String[a];  
        int t = 0;  
        while (itt.hasNext()) {  
            Person p = (Person) itt.next();  
            sort[t] = p.nr;  
            t++;  
        }  
        java.util.Arrays.sort(sort);  
        System.out.println("Navn - ISBN - Nummer - Dato");  
        for(int j = 0; j < t; j++) {  
            Person p = (Person) personm.get(sort[j]);  
            //the p.name is showing p.isbn and p.isbn is showing p.name  
            System.out.print(p.name+" - ");  
            System.out.print(p.isbn+" - ");  
            System.out.print(p.nr+" - ");  
            System.out.print(p.dato);  
            System.out.println();  
        }  
    }  
}  

Full kode:

/* What the librarysystem is doing at the moment!
 * I am able to read the files with books that i already wrote in navn.txt file.
 * I am able to read the data in the file, sort it count all the data in the hashmap Bok bokm
 * I am able to write to the lan.txt file isbn,phonenr,name and current time.
 * The first problem appears when i try to read the data from lan.txt and printout the data
 * the p.name and p.isbn are mixing up. so p.name shows p.isbn and p.isbn shows p.name. 
 * 
 * To test the program and see the problem yourself. The commandline "setup" is
 * javac index.java
 * java index
 * 2 then 1 */
import java.util.*;
import java.io.*;
//import java.text.DateFormat;
import java.text.SimpleDateFormat;

// main meny
class M {
	void meny() {
		System.out.println("(1) Bibliotek");
		System.out.println("(2) Ledige bøker");
		System.out.println("(10) Avslutt");
		menyy();
	}
	void menyy() {
		Scanner sc = new Scanner(System.in);
		String input = sc.next();
		BokInnles bi = new BokInnles();
		UtlanInnlesning ui = new UtlanInnlesning();
		
		try {
			int x = Integer.parseInt(input);
			System.out.println(x);
			switch (x) {
			case 1 : bi.meny(); break;
			case 2 : ui.meny(); break;
			case 10 : break ;
			default :
				System.out.println();
				System.out.println("Error: Velg et tall 1-3 eller 10!");
				meny();
			}
		}
		catch(NumberFormatException nFE) {			    
			System.out.println();
			System.out.println("Error: Ikke et tall!");
			meny();
		}
		sc.close();
	}
}

class index {
	public static void main(String[] args) {
		M m = new M();
		System.out.println("      ### Bibliotek ###");	
		m.meny();
	}
}

// The objectclass that takes bookdata into. No use yet with it. (navn.txt)
class Bok {
	String isbn;
	String title;
	String author;
	String genre;
	Bok(String isbn,String title,String author,String genre) {
		this.isbn = isbn;
		this.title = title;
		this.author = author;
		this.genre = genre;
	}
}

// This objectclass same as above, but takes the data from (lan.txt)
class Person {
	String nr;
	String name;
	String dato;
	String isbn;
	Person(String nr,String name,String dato,String isbn) {
		this.nr = nr;
		this.name = name;
		this.dato = dato;
		this.isbn = isbn;
	}
}

// BokInnles class will read all the bookdata from file navn.txt
class BokInnles {
    HashMap<String,Bok> bokm = new HashMap<String,Bok>();
	BokInnles() {
		try {
		    Scanner scanner = new Scanner(new FileReader("bok.txt"));
		    while (scanner.hasNextLine()) {
		    	String[] col = scanner.nextLine().split(";");
		    	//ISDN;Tittel,Forfatter,Sjanger
		    	String isbn = col[0];
		    	String title = col[1];
		    	String author = col[2];
		    	String genre = col[3];
		    	bokm.put(isbn, new Bok(isbn,title,author,genre));
		    	
		    }scanner.close();
		}
		catch (Exception e) {
		    System.out.println("Error: "+e.getMessage());
		}
	}
    void meny() {
		System.out.println("      ### Bibliotek ###");	
		System.out.println("(1) Oversikt over bøker");
		System.out.println("(2) Utlån");
		System.out.println("(3) Søkefelt");
		System.out.println("(10) Avslutt");
		menyValg();
    }
    void oversikt() {   	
		Iterator<Bok> it = bokm.values().iterator();
		int a = bokm.size();
		System.out.println("Antall bøker: "+a);
		String[] sortname = new String[a];
		int t = 0;
		while (it.hasNext()) {
			Bok b = (Bok) it.next();
		    sortname[t] = b.isbn;
		    t++;
		}
		java.util.Arrays.sort(sortname);
		System.out.println("ISBN - Tittel - Forfatter - Sjanger");
		for(int j = 0; j < t; j++) {
			Bok b = (Bok) bokm.get(sortname[j]);
		    System.out.println(b.title+" - "+b.author);
		}
    }
    void menyValg() {
		Scanner sc = new Scanner(System.in);
		String input = sc.next();
		UtlanUtskrift uu = new UtlanUtskrift();
		try {
			int x = Integer.parseInt(input);
			System.out.println(x);
			switch (x) {
			case 1 : oversikt(); meny(); break;
			case 2 : uu. addPerson(); break;
			case 3 : /*allName();*/ meny(); break;
			case 10 : break ;
			default :
				System.out.println();
				System.out.println("Error: Velg et tall 1-3 eller 10!");
				meny();
			}
		}
		catch(NumberFormatException nFE) {			    
			System.out.println();
			System.out.println("Error: Ikke et tall!");
			meny();
		}
		sc.close();
    }
}

// UtlanInnlesning class read the lan.txt stringdata. and this is where the problem now
// is appearing
class UtlanInnlesning {
    HashMap<String,Person> personm = new HashMap<String,Person>();
    UtlanInnlesning() {
		try {
		    Scanner scanner = new Scanner(new FileReader("lan.txt"));
		    while (scanner.hasNextLine()) {
		    	//ISBN;DATO;MOBILNR;NAVN;
		    	String[] col = scanner.nextLine().split(";");
		    	String isbn = col[0];
		    	String dato = col[1];
		    	String nr = col[2];
		    	String name = col[3];
		    	personm.put(nr, new Person(nr,isbn,dato,name));
		    	
		    }scanner.close();
		}
		catch (Exception e) {
		    System.out.println("Error: "+e.getMessage());
		}
	}
    
    void meny() {
		System.out.println("      ### Utlån ###");	
		System.out.println("(1) Oversikt over lånetagere");
		System.out.println("(2) Oversikt over utlånte bøker");
		System.out.println("(3) Hovedmeny");
		System.out.println("(10) Avslutt");
		menyValg();
    }
    
    void menyValg() {
		Scanner sc = new Scanner(System.in);
		String input = sc.next();
		M m = new M();
		try {
			int x = Integer.parseInt(input);
			System.out.println(x);
			switch (x) {
			case 1 : oversikt(); meny(); break;
			case 2 : meny(); break;
			case 3 : m.meny(); break;
			case 10 : break ;
			default :
				System.out.println();
				System.out.println("Error: Velg et tall 1-3 eller 10!");
				meny();
			}
		}
		catch(NumberFormatException nFE) {			    
			System.out.println();
			System.out.println("Error: Ikke et tall!");
			meny();
		}
		sc.close();
    }
    
    //and this is the method that is making all the trouble
    void oversikt() {   	
		Iterator<Person> itt = personm.values().iterator();
		int a = personm.size();
		System.out.println("Antall utlånte bøker: "+a);
		String[] sort = new String[a];
		int t = 0;
		while (itt.hasNext()) {
			Person p = (Person) itt.next();
			sort[t] = p.nr;
		    t++;
		}
		java.util.Arrays.sort(sort);
		System.out.println("Navn - ISBN - Nummer - Dato");
		for(int j = 0; j < t; j++) {
			Person p = (Person) personm.get(sort[j]);
			//the p.name is showing p.isbn and p.isbn is showing p.name
			System.out.print(p.name+" - ");
			System.out.print(p.isbn+" - ");
			System.out.print(p.nr+" - ");
			System.out.print(p.dato);
			System.out.println();
		}
    }
}

// this class adds data to the lan.txt file
class UtlanUtskrift {
	public static final String DATE_FORMAT_NOW = "dd/MM/yy HH:mm:ss";
	public static String now() {
		Calendar cal = Calendar.getInstance();
		SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT_NOW);
		return sdf.format(cal.getTime());
	}
	
	void addPerson() {
		BufferedWriter bufferedWriter = null;
		try {
    		Scanner sc = new Scanner(System.in);
			//Construct the BufferedWriter object
			bufferedWriter = new BufferedWriter(new FileWriter("lan.txt",true));  
			//Start writing to the output stream
    		System.out.print("ISBN: ");
    		String isbn = sc.next();
    		System.out.print("Mobil Nr: ");
    		String nr = sc.next();
    		System.out.print("Ditt Navn: ");
    		String name = sc.next();
    		//Utskrift blir ISBN;dag/måned/år time:minutt:sekund;nr;navn
			bufferedWriter.write(isbn+";"+now()+";"+nr+";"+name+";");
			bufferedWriter.newLine();
			sc.close();
			System.out.println("Følgende data er lagt til!");
			System.out.println("ISBN: "+isbn);
			System.out.println("Navn: "+name);
			System.out.println("Nummer: "+nr);
			System.out.println("Dato: "+now());
		}
		catch (IOException ex) {
			ex.printStackTrace();
		}
		finally {
			//Close the BufferedWriter
			try {
				if (bufferedWriter != null) {
					bufferedWriter.flush();
					bufferedWriter.close();
				}
			}
			catch (IOException ex) {
				ex.printStackTrace();
			}
		}
	}
}

[Greg Charles]

This might be the problem:

personm.put(nr, new Person(nr,isbn,dato,name));

and

Person(String nr,String name,String dato,String isbn)

It's always good to check the obvious stuff first!

[Winston Gutkowski]

Tor Ludgivsen wrote:Hello! Im having a problem with my library system...

Tor,

1. For future reference, try to only post code that is relevant to your problem; it saves us from having to plough through a lot of irrelevant information and will help you get answers quicker.

And since Greg's already shown you your actual error, here are a few general tips:

2. Don't use Strings for anything except strings of characters; and the only field in your Person class that meets that criterium is name. For more information, see this page.

3. Avoid using single-character names for anything except loop variables. For example:
int a = personm.size();
Why not:
int size = personm.size();
(or the equivalent in Norwegian)?
Anything you can do to make your programs more readable is a good thing.

4. Your sort method is a good example of overthinking (and don't worry; it's a common beginner's mistake ):
First: Lists are usually better than arrays; and you can create a List directly from a Collection.
Second: You can sort an ArrayList just as quickly with Collections.sort() as you can an array with Arrays.sort().
Third: You can sort objects any way you like with a Comparator (java.util.Comparator). If you haven't heard about them yet, I suggest you read up on them.
Fourth: Get into the habit of using for-each loops. They save you all that mucking about with Iterators.

Put that all together and you get something like:

public class PersonsByNumber
   implements Comparator<Person>
{
   @Override
   public int compare(Person p1, Person p2) {
      return p1.nr.compareTo(p2.nr);
   }
}

void oversikt() {
   PersonsByNumber byNumber = new PersonsByNumber();
   List<Person> people = new ArrayList<Person>(personm.values());
   Collections.sort(people, byNumber);
   System.out.println("Navn - ISBN - Nummer - Dato");  
   for(Person p : people) {  
      System.out.print(p.name+" - ");
      //etc.
   }  
}

HIH

Winston

[Tor Ludgivsen]

Greg Charles thanks a lot. and i did look at it, but did not know that it matters the order i put data in.

Winston Gutkowski. thanks a lot, will follow your advices and try the new stuff you told me. is there some place on the forum where you can post your product, and just get advices on how to improve things?

[Campbell Ritchie]

Tor Ludgivsen wrote: . . . is there some place on the forum where you can post your product, and just get advices on how to improve things?

Yes. Here