How to convert linkedlist to array using `toArray()`?

Question

I do not know how to convert a linked list of doubles to array. Please help me find the error.

import java.util.*;
public class StackCalculator {


  private         


        

Answer 1

The List#toArray() of a List returns Double[]. The Double[] isn't the same as double[]. As arrays are objects, not primitives, the autoboxing rules doesn't and can't apply here.

Either use Double[] instead:

Double[] array = list.toArray(new Double[list.size()]);

...or create double[] yourself using a simple for loop:

double[] array = new double[list.size()];
for (int i = 0; i < list.size(); i++) {
    array[i] = list.get(i); // Watch out for NullPointerExceptions!
}