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Dynamic use of arrays
Arrays example from a Well House Consultants training course
More on Arrays [link]

This example is described in the following article(s):
   • Java is a dynamic language .... (and comparison) - [link]

This example references the following resources:
http://www.wellho.net/mouth/1498_.html

Source code: rowby.java Module: J705

/* See http://www.wellho.net/mouth/1498_.html for details

Although you cannot extend an array in Java (but you can in
java.lang.util objects such as a Vector and an ArrayList) you
can re-allocate a new array to an existing name. */


public class rowby {

public static void main (String [] args) {

/*
Pascal's Triangle - row by row using previous
and current rows in arrays of those names
*/


        int rows = 15;
        int [] previous, current;
        previous = new int[0];

        for (int k=0; k<rows; k++) {

// Calculate current row based on previous one

                current = new int[previous.length+1];
                current[k]= current[0] = 1;
                for (int j=1; j<previous.length; j++) {
                        current[j] = previous[j-1] + previous[j];
                }

// Output the current row

                for (int c=0; c<current.length; c++) {
                        System.out.print(current[c]);
                        System.out.print(" ");
                }
                System.out.println();

// Make the current row into the previous one

                previous = current;
        }
}
}

/*

Sample output:

[trainee@snowdrop java08]$ java rowby
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1
1 8 28 56 70 56 28 8 1
1 9 36 84 126 126 84 36 9 1
1 10 45 120 210 252 210 120 45 10 1
1 11 55 165 330 462 462 330 165 55 11 1
1 12 66 220 495 792 924 792 495 220 66 12 1
1 13 78 286 715 1287 1716 1716 1287 715 286 78 13 1
1 14 91 364 1001 2002 3003 3432 3003 2002 1001 364 91 14 1
[trainee@snowdrop java08]$

*/

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to Program in Java
 * Java Bootcamp
 * Java Programming for the Web
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Java and associated technologies are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Arrays" training module. You'll find a description of the topic and some other closely related examples on the "Arrays" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

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