Java Array's.... Making An array bigger???

Tru_Messiah · 05-17-2004, 02:05 AM

Ok I have an array full of 10 objects. This array is called carArray..

Now I wish to add a new object to the array but am having trouble.

I started off thinking that I should create a tempoary array one index bigger then the current array, copy the information from the first array to the second array and then create the original array again but one bigger then copy the information from the temp array to the original... however when I try to create the original array again it says that it already exsists and wont compile..

here is my "copying array" code...

Car [] tempArray;
tempArray = new Car [carArray.length+1];
System.out.print(" Length = " + tempArray.length);

for (int x = 0; x <carArray.length; x++)

{
tempArray[x] = carArray[x];
}

System.out.print(tempArray[9].getMillage()); // to test objects been copied correctly...

Now this works fine I'm just not sure what to do now... I thought about maybe recreating the first array like this...

Car [] carArray;
carArray = new Car [tempArray.length];

but it already exsists and so wont compile,how do I increase the lenghth of the original array???

thanks alot...

Tru_Messiah · 05-17-2004, 03:52 AM

Never mind... i was being very stupid.. I don;t need to put

Car [] carArray;

in again when editing the length of the first array//

this is my first time at using arrays so I don't think i'll be making that mistake again... oh well... onto writing to a file now... looks scary..

villie · 05-17-2004, 07:20 AM

Well the size of the arrays in Java is static and has to be determined at the compile time.
You cant change at the run time . You can use ArrayList or Vectors for dynamically resizing your object container.
What you are doing , it will make a new array and you will lose the original array. So i dont think it is the best thing to do.

Regards
Villie

Tru_Messiah · 05-17-2004, 07:28 AM

Nah it works cool, I move all the data (objects) to a temp array first and then resize the original array. Then after that just copy all the data back.

llama_meme · 05-17-2004, 08:51 AM

That will work, but it's very inefficient. You should use the Vector class.

Alex

dave_starsky · 05-17-2004, 03:14 PM

First off, ArrayList is the way to go

secondly, this will make your array bigger

Code:

class NameHandler
{
//let us start by creating our array
String [] nameArray = new String [3];

   public static void main(String [] args)
   {
      //lets add some names to our array
      nameArray [0] = "Dave";
      nameArray [1] = "Steve";
      nameArray [2] = "Mary";

      //it should be full now, so we need to extend it
      extendArray();

      //now we can add some more names
      nameArray [3] = "Jo";
      nameArray [4] = "Richard";
   }

   private static void extendArray()
   {
       //create  a new array 3 larger than the original
       String tempArray = new String [nameArray.length + 3];

       //copy all of the data to the new array
       for(int i=0; i<nameArray.length; i++)
           tempArray [i] = nameArray [i];

       //since the variables are just pointers we just need to make the 
       //nameArray point to our new array
       nameArray = tempArray;
   }
}

Looking_Lost · 05-17-2004, 05:38 PM

Or a slight variation

System.arraycopy(originalArray,0,tempArray,0,originalArray.length);

originalArray=tempArray;

why not use a dynamic class though

Tru_Messiah · 08-15-2016, 05:18 PM

Because I was a stupid noob who was doing his first term of Java programming and didn't know what I was doing!

EDIT - Oh and apologies for the late reply.

sundialsvcs · 08-16-2016, 08:11 AM

Quote:

Originally Posted by Tru_Messiah

Because I was a stupid noob who was doing his first term of Java programming and didn't know what I was doing!

Hey ... "not (yet) knowing what you're doing" is just par-for-the-course. No reason to speak ill of yourself.

After all, this is

Java

we are talking about here!

But, anyhow: IMHO, most of the time you should be using container classes, not fixed-size things such as "true arrays" (which Java does support, while PHP, say, does not). The implementation of these classes will handle all of the usual operations: insert, append, delete, push, shift, count, empty, retrieve. And they will do so very, very efficiently. (Well, at least as efficiently as Java

can manage to do anything at all ...) *koff, koff ...*

And, really, the same is now true of many other languages: C#, Delphi, C++, etc. If the language provides containers, then you should use them most of the time. It's also important to understand a little bit about the underlying implementation of each class, because, "every data structure is some kind of compromise."

grail · 08-16-2016, 08:46 AM

So I have heard of replying late ... but 12 years is a bit of stretch to call late

sundialsvcs · 08-17-2016, 01:05 PM

Yeah, I knew that it was an old thread, but the same issues keep coming up again and again.

grail · 08-17-2016, 01:45 PM

@sundialsvcs - I found your reply useful. Was more commenting on the OP's late reply