• Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Liutauras Vilda
  • Tim Cooke
  • Jeanne Boyarsky
  • Bear Bibeault
Sheriffs:
  • Knute Snortum
  • paul wheaton
  • Devaka Cooray
Saloon Keepers:
  • Tim Moores
  • Stephan van Hulst
  • Ron McLeod
  • Piet Souris
  • Ganesh Patekar
Bartenders:
  • Tim Holloway
  • Carey Brown
  • salvin francis

Multidimensional Arrays

 
Ranch Hand
Posts: 35
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I understand how the Multidimensional Arrays are built.
My question is about this: Line 22
months = years[1];
What happens here?
What is the value of years[1]?
And any additional information that will help me understand multidimensional arrays
Thanks
public class ArrayStuff
{
public byte[] b;
public int i[];
public ArrayStuff[][] testme;
float years[][];
float months[];
ArrayStuff()
{
years = new float[3][4];
months = new float[3];
years[1][1] = 2000;
months[1] = 1;
months[2] = 2;
months[2] = years[1][3];
months[1] = years[2][2];

months = years[1];//I need help understanding



System.out.println(months[3]);
float f = 3;
months[(int)f] = 2;
}
public static void main(String args[])
{
ArrayStuff arrayStuff = new ArrayStuff();
System.out.println("Joe Sample " + arrayStuff.months[3]);
System.out.println("Smooth Jazz " + arrayStuff.years[1][3]);
}
}
 
mister krabs
Posts: 13974
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
years[1] contains a float array.
 
Jacob Michaels
Ranch Hand
Posts: 35
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I still am unclear on that. can you explain how that is possible. And where does the value of 3 come from.
Does that line create another element in the months array?
Thank you
 
Ranch Hand
Posts: 3451
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi Jacob,
A multi-dimensional array is simply an array of arrays. So if I have a two-dimensional array, then all of the members of that array are one-dimensional (simple) arrays. If I have a three-dimensional array, then all of its members are two-dimensional. So in general, an array of N dimensions has for its elements arrays of N-1 dimensions for all N >= 1 assuming that an array of 0 dimensions is a simple element.
Hope this clears it up,
Michael Morris
 
Jacob Michaels
Ranch Hand
Posts: 35
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Yes that helps.
years = new float[3][4];
months = new float[3];
months = years[1];
float f = 3;
months[(int)f] = 2;
I just can't see how this adds aother element in the months[]. I was expecting an out of bounds error.
Not sure of the value that years[1]
Thank for the responses.
I am very impressed with this forum!
 
Michael Morris
Ranch Hand
Posts: 3451
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator


years = new float[3][4];
months = new float[3];
months = years[1];
float f = 3;
months[(int)f] = 2;
I just can't see how this adds aother element in the months[]. I was expecting an out of bounds error.
Not sure of the value that years[1]


Arrays are stored in row major order. For your example the years[][] array consists of 3 simple arrays of 4 elements each. So when you set the months array equal to years[1], both months and years[1] now refer to the same array of four elements. Take a look at this code:

Here's the output:

Note that months[3] and years[1][3] now contain the float value of 2.0. That makes sense because they each refer to the same element.
Michael Morris
 
Jacob Michaels
Ranch Hand
Posts: 35
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thank you that helps!
I could actually say:
float[]months = years[0];
or
float[]months = years[2];
and it would mean the same thing.
Months would have 4 elements the same as the 3 simple arrays that years have.
I was reading that when you assign a two dimensional array:
example:
years[rows][columns];
that was confusing me with have 3 simple arrays with 4 elements.
Thank you for all for the reponses!
[ March 23, 2003: Message edited by: Jacob Michaels ]
 
Michael Morris
Ranch Hand
Posts: 3451
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator


I could actually say:
float[]months = years[0];
or
float[]months = years[2];
and it would mean the same thing.


Not exactly. Remember, that years[0] and years[2] are two distinct arrays. Also, you can have non-symettrical multi-dimensional arrays where the individual arrays are not all the same size. Consider this:

Here's the output:

Michael Morris
 
I think I'll just lie down here for a second. And ponder this tiny ad:
professionally read, modify and write PDF files from Java
https://products.aspose.com/pdf/java
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!