issue creating a double array list

Question

Is there any reason the fallowing code would give A compile error ?

Import java.util.*;

public class Storageclass
// class used to store the Student data 
{
 // creates the private array list needed. 
 private ArrayList<String> nameList = new ArrayList<String>();
 private ArrayList<double> GPAList = new ArrayList<double>();
 private ArrayList<double> passedList = new ArrayList<double>();
}

this is in a class access by a main file there is more in the class by it not part of this error. when I run this the two double arrayList give me this error.

Storageclass.java:8: error: unexpected type
 private ArrayList<double> GPAList = new ArrayList<double>(1);
                   ^
  required: reference
  found:    double

I am not sure why or what that error means any help would be appreciated.

~ Thanks for the help was a embarrassingly novice mistake I made, but hope full this can help some other person.

Did you at least try to search for this issue on the net before asking? — Luiggi Mendoza, Nov 18 '13 at 02:31

Pshemo · Answer 1 · 2013-11-18T03:04:47.767

Since all generic types <T> are erased at runtime to Object every type you put in place of T must also extend Object. So you can't set T to be primitive type like double but you can use its wrapper class Double. Try this way:

private List<Double> passedList = new ArrayList<Double>();

or since Java7 little shorter version

private List<Double> passedList = new ArrayList<>();

Also don't worry if you try to add variable of double type to such array since it will be autoboxed to Double.

score 2 · Answer 2 · answered Nov 18 '13 at 02:31

2

Primitive types cannot be used as generic type arguments. Use the wrapper type Double (or whichever is appropriate).

answered Nov 18 '13 at 02:31

Sotirios Delimanolis

274,122
60
696
724

score 2 · Answer 3 · answered Nov 18 '13 at 02:31

2

Use ArrayList<Double> instead of ArrayList<double>.

answered Nov 18 '13 at 02:31

brettw

10,664
2
42
59

1

In fact, OP should use `List` instead of `ArrayList`. – Luiggi Mendoza Nov 18 '13 at 02:32
@LuiggiMendoza Why should a `List` be used instead of an `ArrayList`? – Justin Nov 18 '13 at 02:48

score 0 · Answer 4 · answered Nov 18 '13 at 02:32

0

cant be primitive type

private ArrayList<double>

use Double

private ArrayList<Double>

answered Nov 18 '13 at 02:32

Paul Samsotha

205,037
37
486
720

issue creating a double array list

4 Answers4

Linked