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May 6th, 2007

adding to a dynamic array size...

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I can't figure how to get this going, for every object I create I want to add that to the existing array. I read about arraycopy but I don't know how to increase the existing size of the array and always end up with array out of index error...

java Syntax (Toggle Plain Text)
A a1 = new A(1, 2, "test");
 
size = 1;
sizeCounter = 1;
A a[] = new A[size];
a[0] = a1;
 
A a2 = new A(3, 4, "test2");
 
sizeCounter++;
if (sizeCounter>=size){
size++;}
 
A[size-1] = a2;
A a1 = new A(1, 2, "test");

size = 1;
sizeCounter = 1;
A a[] = new A[size];
a[0] = a1;

A a2 = new A(3, 4, "test2");

sizeCounter++;
if (sizeCounter>=size){
size++;}

A[size-1] = a2;

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rugae

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May 6th, 2007

Re: adding to a dynamic array size...

Why not encompass your existing class around the ArrayList. Then just access the .add() method?

iamthwee

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May 7th, 2007

Re: adding to a dynamic array size...

iamthwee is right, you should be using ArrayList. You cannot increase the size of an existing array. You have to create a new array that is one larger than the current array, then you can use System.arraycopy to copy the existing elements from the old to the new array, than add the new element.

masijade

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May 7th, 2007

Re: adding to a dynamic array size...

Doh! Ok, then, I'll just increase the size of the array. I was doing somethig similar to below, everything is done but I thought it would be neat idea to increase the array dynamically.

prompt user for input
checkinput()
if no dupe add to array
else error msg

Last edited by rugae; May 7th, 2007 at 7:44 am.

rugae

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Re: adding to a dynamic array size...

Click to Expand / Collapse Quote originally posted by rugae ...

Doh! Ok, then, I'll just increase the size of the array. I was doing somethig similar to below, everything is done but I thought it would be neat idea to increase the array dynamically.

prompt user for input
checkinput()
if no dupe add to array
else error msg

You obviously missed my post then...

iamthwee

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Aug 14th, 2009

Re: adding to a dynamic array size...

Guys you can use

import java.util.List;

List <String> wordset = new ArrayList <String>();

usimg this you can get dynamic arrays working well...

pasanindeewara

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Aug 14th, 2009

Re: adding to a dynamic array size...

You could even use Vector class.
Its implementation is much simpler.
Its in java.util package

harsh2327

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Aug 15th, 2009

Re: adding to a dynamic array size...

Click to Expand / Collapse Quote originally posted by rugae ...

Doh! Ok, then, I'll just increase the size of the array. I was doing somethig similar to below, everything is done but I thought it would be neat idea to increase the array dynamically.

prompt user for input
checkinput()
if no dupe add to array
else error msg

you need to know that the array that you use in java is not flexible to increase the size of the array by itself, the array is a STATIC data structure.

if you make

Java Syntax (Toggle Plain Text)
int [] arr = new int[10];
int [] arr = new int[10];

this array will remain in your scope of length 10, unless you make a new array that is nor related to that one and of bigger size and then put the elements of the first array in the second array and then make the first array point to the second array.

Java Syntax (Toggle Plain Text)
int [] arr = new int[10];
/* put data in the 10 elements of arr
-----
----
*/
int []arr2 = new int[arr.length * 2];
//copy the elements of arr to the first 10 elements of arr2
arr = arr2;
int [] arr = new int[10];
/* put data in the 10 elements of arr
-----
----
*/
int []arr2 = new int[arr.length * 2];
//copy the elements of arr to the first 10 elements of arr2
arr = arr2;

or you can easily use arrayList as they told you, which already does that.

Last edited by eng.M4AH; Aug 15th, 2009 at 12:14 pm.

eng.M4AH

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