Help @ Java

[Ben_Dover]

package banksystem;

import java.io.File;
public class test {
    static Person[] p;
    public static void main(String[] args) {

        final File f = new File("bankomat.dat");
        BankSystem bs = new BankSystem();
        setUPUser("Anders", "300", 1);
        setUPUser("Stig", "100", 1);
        bs.saveDATFile(f);
    }

    protected static int checkID(int newID)
    {
        [B]for (Person np : p)[/B]
        {     
            if (newID == np.getID())
            {
                checkID(newID + 1);
            }
            else
            {
                return newID;
            }
        }
        return newID;
    }

    protected static void setUPUser(String newMoney, String newName, int newID)
    {
        p[0] = new Person(newName, newMoney, checkID(newID));
    }

    private void typeUsers()
    {
        for (Person np : p)
            System.out.println(np.toString());
    }
}

package banksystem;

import java.io.Serializable;
import java.util.ArrayList;

public class Person implements Serializable {

    static int id;
    ArrayList<String> a;

    public Person()
    {
        setID(1);
        this.a = new ArrayList<String>();
        setName("Per");
        setMoney("100");
    }

    public Person(String newName)
    {
        setID(BankSystem.getK());
        this.a = new ArrayList<String>();
        setName(newName);
        setMoney("0");
    }

    public Person(String newName, String newMoney, int newID)
    {
        this.a = new ArrayList<String>();
        setName(newName);
        setMoney(newMoney);
        setID(newID);
    }

    protected static void setID(int setNewID)
    {
        id = test.checkID(setNewID);
    }

    private void setName(String name)
    {
        a.add(0, name);
    }

    private void setMoney(String money)
    {
        a.add(1, money);
    }

    public int getID()
    {
        return id;
    }

    public String getName()
    {
        return a.get(0);
    }

    public String getMoney()
    {
        return a.get(1);
    }

    @Override
    public String toString()
    {
        return ("The name of ID " + getID() + " is: " + getName() + ". " + getName() + " has " + getMoney() + " Swedish kronor.");
    }
}

Throws me nullpointerexception, why?

Exception in thread "main" java.lang.NullPointerException
at banksystem.test.checkID(test.java:22)
at banksystem.test.setUPUser(test.java:39)
at banksystem.test.main(test.java:15)
Java Result: 1

[sunde887]

It looks like you never initialize p, it's just an array declaration without an initialization.

There is also quite a few other problems with this code.

[j2me64]

the Person[] p is never initialized, but even if you initialize this array the first time you make a call to checkID there are no elements in the array so the np.getID() will cause the NullPointerException. make sure np.length > 0 is true!

[DarrylBurke]

...

You seem to be establishing a trend of never returning to the threads you start, never replying to the responses. Not the best way to get help on a forum, that.

db