creating array without declaring the size - java

Question

i've digging around about the same issue but i couldn't find the same as i had

i want to create an array without declaring the size because i don't know how it will be !

to clear the issue i'd like to give you the code that i'm looking up for

public class t
{
 private int x[];
 private int counter=0;
 public void add(int num)
 {
   this.x[this.counter] = num;
   this.counter++;
 }
}

as you see the user could use the add function to add element to the array 10000 times or only once so it's unknown size

Answer 1

Using Java.util.ArrayList or LinkedList is the usual way of doing this. With arrays that's not possible as I know.

Example:

List<Float> unindexedVectors = new ArrayList<Float>();

unindexedVectors.add(2.22f);

unindexedVectors.get(2);

Answer 2

You might be looking for a List? Either LinkedList or ArrayList are good classes to take a look at. You can then call toArray() to get the list as an array.

Answer 3

As others have said, use ArrayList. Here's how:

public class t
{
 private List<Integer> x = new ArrayList<Integer>();

 public void add(int num)
 {
   this.x.add(num);
 }
}

As you can see, your add method just calls the ArrayList's add method. This is only useful if your variable is private (which it is).

Answer 4

Once the array size is fixed while running the program ,it's size can't be changed further. So better go for ArrayList while dealing with dynamic arrays.

Answer 5

How about this

    private Object element[] = new Object[] {};

Answer 6

I think what you really want is an ArrayList or Vector. Arrays in Java are not like those in Javascript.