havin problems with Object array

[Abhi Chat]

I want to have an 2 dimen dynamic object array to get the data from the file and then write it to the Jtable. But I dont want to give the size...

Object [][] o = new 0bject[][];
Like for each iteration

o[i][j]="somedata"

But as it looks it gives me a null pointer exception, could i someway get the things done avodin the exception....

[Marlene Miller]

Hi Abhi,

You can store things in a 1-dim dynamic ArrayList. Then convert the list to a 1-dim array.

import java.util.*;
 
class Test {
   static int numFields = 3;
 
   public static void main(String[] args) {
      ArrayList list = new ArrayList();
 
      Object[] field = new Object[numFields];
      field[0] = "apple";
      field[1] = new Integer(100);
      field[2] = "c";
      list.add(field);
 
      field = new Object[numFields]; // a new array object (*)
      field[0] = "d";
      field[1] = new Integer(20);
      field[2] = "f";
      list.add(field);
 
      Object[] data = list.toArray(new Object[0][0]);
      Object[][] obj = (Object[][])data;
 
      String s = (String)obj[0][0];
      Integer i = (Integer)obj[0][1];
 
      System.out.println(s);
      System.out.println(i.intValue());
   }
}

I forgot to create a new Object[] at (*). For some reason, I lost the first array. But I am too sleepy to figure out why.

[Abhi Chat]

Thanx Marlene...

Actually I also figured similar code through vectors:

                Vector vp = new Vector();
Vector v = new Vector();
Vector v1 = new Vector();



v.addElement("Abhi");
v.addElement("Nir");
v.addElement("Saby");
v.addElement("Rupesh");
v.addElement("Same");



Object [] vec=v.toArray();
Object [] vec1=v1.toArray();

vp.addElement(vec);
vp.addElement(vec1);

Object[][] fin =new Object[vp.size()][v.size()];

for(int i=0;i<vp.size();i++)
{
   for(int j=0;j<v.size();j++)
   {
   fin[i][j]=vec[j];
   System.out.println(fin[i][j]);  
   }
   
}   

 

 

[Marlene Miller]

Abhi, did you know that Vector is a "legacy" container class. It has been retrofited to be a part of the Java API collections framework. All methods that access the contents of a Vector are synchronized.

My impression is in books authors use ArrayList instead of Vector. I'd use ArrayList unless I really wanted synchronized methods.

[Abhi Chat]

Thanx Marlene..for pointing out that....

abhi