Create and iterate a list of Strings in Java

Question

I'm trying to create list of arrays, dynamic in size, add elements and iterate through them when I finish. Currently my code is:

    String activities = "SELECT DISTINCT phoneactivity from ContextTable030313";
    ArrayList<String> myActivities = new ArrayList();

    Cursor cursor2 = db.rawQuery(activities, null);
    // looping through all rows and adding to list
    if (cursor2.moveToFirst()) {
        do {
            myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));

        } while (cursor2.moveToNext());
    }

Yet it fails to run in the do loop. I believe I am declaring something incorrectly and I get the following warnings:

- ArrayList is a raw type. References to generic type ArrayList<E> should be parameterized
    - Avoid object allocations during draw/layout operations (preallocate and reuse instead)
    - Type safety: The expression of type ArrayList needs unchecked conversion to conform to 
     ArrayList<String>

yet I do not understand why this does not work.

pre Java 7, <String> should come in both sides. ie new ArrayList<String>() as well — rajesh
– rajesh, Commented Mar 5, 2013 at 6:38
I did that and I still get the following warning: "Avoid object allocations during draw/layout operations (preallocate and reuse instead)" AND my code still fails in the do loop.... — WildBill
– WildBill, Commented Mar 5, 2013 at 6:41
It sounds like that warning is telling you that you're accessing the database from the wrong place/thread. Maybe if you hit the database and initialize myActivities in the correct place, your loop will work better. That being said, I have no idea what framework/platform you're using... Swing? Android? — jahroy
– jahroy, Commented Mar 5, 2013 at 6:43
Try to print cursor.getString(cursor2.getColumnIndex("ts")) in your console what exactly printing this line. — subodh
– subodh, Commented Mar 5, 2013 at 6:43

npinti · Accepted Answer · 2013-03-05 06:39:05Z

1

The problem seems to be this:

Type safety: The expression of type ArrayList needs unchecked conversion to conform to ArrayList

Which points out to this line of code:

ArrayList<String> myActivities = new ArrayList();

You should change that line to this:

ArrayList<String> myActivities = new ArrayList<String>();

On a different note, you could replace this code segment:

  if (cursor2.moveToFirst()) {
        do {
            myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));

        } while (cursor2.moveToNext());
    }

With this:

  while (cursor2.moveToFirst()) {       
        myActivities.add(cursor.getString(cursor2.getColumnIndex("ts")));       
    }

answered Mar 5, 2013 at 6:39

npinti

52.2k5 gold badges74 silver badges98 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

PermGenError · Accepted Answer · 2013-03-05 06:38:27Z

0

change your arrayList declaration such that it accepts parameterized type during constructor invokation.

ArrayList<String> myActivities = new ArrayList<String>();

If you use java 7 or above:

ArrayList<String> myActivities = new ArrayList<>();

You don't need to declare the parametreized type during constructor invokation due to *Type inference*but you still need to declare empty <>.

answered Mar 5, 2013 at 6:38

PermGenError

46.5k8 gold badges90 silver badges107 bronze badges

1 Comment

WildBill Over a year ago

I did that and I still get the following warning: "Avoid object allocations during draw/layout operations (preallocate and reuse instead)" AND my code still fails in the do loop....

Collectives™ on Stack Overflow

Create and iterate a list of Strings in Java

2 Answers 2

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related