How to use dynamic types: []

Question

Hello!
I don't know to use dynamic types: []
for example:
          double[] tmp = new double[2];
          ArrayList<double[]> tmp2= new ArrayList<double[]>();
          for(int i = 0; i<5; i++){
               tmp[0] = i;
               tmp[1] = i+1;
          tmp2.add(tmp);
*Why all tmp2 members are similar to the last value of tmp?
*How can I keep all the values from
          tmp[0] = 0;
          tmp[1] = 1;
to
          tmp[0] = 4;
          tmp[1] = 5;
in tmp2?
Thanks!

Answer 1

800512 wrote:
I don't know to use dynamic types: []I'm going to take a punt here, and assume that you are talking about using a List as a dynamically extending array, in which case you need to learn about defining element types:ArrayList<double[]> tmp2= new ArrayList<double[]>();is wrong. You cannot put primitive types in angled brackets; only class or interface names. Therefore the proper definition is:ArrayList<Double[]> tmp2= ...
*Why all tmp2 members are similar to the last value of tmp?Because you've only added one element to tmp2.
*How can I keep all the values from...in tmp2?Look at your loop and write out on a piece of paper what you think it's doing. Hopefully that'll give you the answer.
If you do indeed want each element in the List to contain a pair of values, you're going to have to work out some way of adding to your List once for every two values you're inputting. I suggest you think about that too.
Winston