Vector Collection

[V Bose]

Aim : Create a 2 dimensional array data structure @ runtime.
Premise : New to Java!
What I tried :
int i=0;
Vector Correlation;
Correlation = new Vector();
while (i < NRows)
{
Correlation.addElement(new Vector());
i++;
}
((Vector)Correlation.get(0)).add("10"); //Correlation[0][0]=10
((Vector)Correlation.get(0)).add("5"); //Correlation[0][1]=5

Question 1 : Is there another(less painful) way I can simulate a flexible, m-dimensional array @ runtime.
Question 2 : Am I using the right way to access the Vector of Vectors in Correlation

[Ernest Friedman-Hill]

What you're doing is basically sound. To make it less painful, you would encapsulate the whole thing in a class. This class could use Vector in its implementation, or it might even just use arrays.
The class (call it Matrix) could have methods like

public class Matrix {
  public Matrix(int rows, int columns) { ... }
  public Object get(int row, int col) { ... }
  public void set(int row, int col, Object o) { ... }
  public void resize(int newRows, int newColumns) { ... }
  // ... 
}

Then you could say

Matrix m = new Matrix(3, 3);
m.set(0, 0, "a");
m.set(0, 1, "b");
String datum = (String) m.get(0, 1);

Finally: note that there is a very strongly respected coding standard that says Java variable names should begin with a lowercase letter; writing "Correlation" with an uppercase letter makes your code harder to read for those of us who are used to reading Java code.

[V Bose]

OOps. Soory about the capitalization of variables...
If you notice, in my earlier piece of code...
((Vector)correlation.get(0)).add("10"); //correlation[0][0]=10
adds the element "10" to the vector of vector.
But how do I modify this value "10" now ?

[Ernest Friedman-Hill]

Using my Matrix class, or using your original code? In the Matrix class, you just call set(0, 0, "20"). In your approach, you'd have to do something like
((Vector)correlation.get(0)).setElementAt("20", 0);