Tree

[zealman]

import java.util.*;
import java.io.*;
import java.math.*;
import java.awt.event.*; 
 
class Node
{
    String ortu,isi;
    int jumanak,jumchild;
    Node child[] = new Node[5];
public Node(String parent, String a)
    {
        ortu=parent;
        isi=a;
                jumanak=jumchild;
    }
}
 
public class tree 
{
private Node root;
 
       private boolean isEmpty()
       {
        return (root == null);
       }
 
       public void insert(String x,String y, int pos)
       {
        int coba;
        coba = 0;
                Node temp = new Node(x,y);
        if (isEmpty())
        {
            root = temp;
                        System.out.println("root awal:"+root.isi); 
                        root.jumchild=0;
        }
 
        else 
        {
                        root.jumchild++;
                        System.out.println("jum child:"+root.jumchild+"y:"+y); 
            Node cursor = root,
            parent = null;
                        coba = 1;
            for ( int i=1;i<root.jumchild;i++)
                        {
                if ( root.child[i-1].isi == y )
                                {
                                  coba = 0;   
                  System.out.println("child ke "+root.child[i-1].isi+" sama dengan "+y);                              
                                }
                else
                                {
                                 coba = 1;
                                }
 
            }
             if ( coba == 1 )
             {
            while (cursor != null)
            {
                parent = cursor;
                cursor = cursor.child[pos];
                parent.child[pos] = temp;
                System.out.println("parent : "+root.child[pos].ortu+" isi : "+root.child[pos].isi);
            }
                     }
        }
    }
 
    public void level2()
    {
        Node tempo=new Node("C1","C1.1");
        Node curs=root.child[0], ortu=null;
        ortu=curs;
        curs=curs.child[0];
        ortu.child[0] = tempo;
    System.out.println("parent : "+root.child[0].child[0].ortu+" isi : "+root.child[0].child[0].isi);
    }
 
    public void baca()
    {
        String file="bacatulis.txt";
        String [] kolomtxtcek;
        String baristxtcek,a,b;
        int c;
        int jum=0;
        try
        {
            BufferedReader baca = new BufferedReader(new FileReader(file));
            while ((baristxtcek = baca.readLine()) != null)
            {
                kolomtxtcek = baristxtcek.split(",");
                a=kolomtxtcek[0];
                b=kolomtxtcek[1];
                c=Integer.parseInt(kolomtxtcek[2]);
                insert(a,b,c);
            jum++;
            }    
        }
        catch (IOException e) 
        {
             System.err.println("Error: " + e);
        }
        System.out.println(jum);
    }    
 
    public static void main (String[] args) 
    {
        tree pohon=new tree();
    pohon.baca();
        pohon.level2();    
    }
 }
 

this is the error output......
Exception in thread "main" java.lang.NullPointerException
at tree.insert(tree.java:55)
at tree.baca(tree.java:106)
at tree.main(tree.java:137)

[jkmyoung]

You're incrementing only the root's # of children
root.jumchild++;
even when you add the node to one of the root's children. I don't entirely get your algorithm for adding nodes, but you want to instead increment the child count of the node you actually add the new node to.