java.lang.ClassCastException: java.lang.Double cannot be cast to java.lang.String

Question

I have done with code in Android:

List<String> spinnerArray =  new ArrayList<String>();
for (int i = 0; i < items.size(); i++) {
    LinkedTreeMap<String, String> item = (LinkedTreeMap) items.get(i);

    // THIS LINE THROW EXCEPTION
    double d = Double.parseDouble(item.get("id").toString());

    locations.put(Integer.parseInt(item.get("id")), item.get("name"));
    spinnerArray.add(item.get("name"));
}

I get the error when I define the "d" variable.
The strange thing is if I run the same line in the debug I get the double value I need.

UPDATE ANSWER

On the debug window I have:

items.get(i) = {LinkedTreeMap@5317} size = 5
0 = {LinkedTreeMap$Node@5378} "id" -> "1.0"
    key = "id"
    value = {Double@5384} "1.0"

Correct me if I'm wrong but, item.get("id") will return you a String so why use .toString() ? — vincrichaud
– vincrichaud, Commented Mar 13, 2018 at 12:04
You don't need toString(). Also, is it a double or an integer? You're parsing the ID twice — OneCricketeer
– OneCricketeer, Commented Mar 13, 2018 at 12:04
To try everything :( I already tried without .ToString() and I get the error, so I tried with .ToString() — Giacomo M
– Giacomo M, Commented Mar 13, 2018 at 12:05
The only casting is happening at (LinkedTreeMap) items.get(i) . What does items contain? — Lance Toth
– Lance Toth, Commented Mar 13, 2018 at 12:05

sarkasronie · Accepted Answer · 2018-03-13 12:13:20Z

2

Seems that LinkedTreeMap items is of type [String, Object] and not [String, String].

So your code should look like:

LinkedTreeMap<String, Object> item = (LinkedTreeMap) items.get(i);

Thanks to Timothy Truckle.

edited Mar 13, 2018 at 12:13

answered Mar 13, 2018 at 12:09

sarkasronie

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1 Comment

Timothy Truckle Over a year ago

Close, but the OP missuses the map as a "custom Object type" so that different keys have different value types. Therefore item must be LinkedTreeMap<String, Object>

Timothy Truckle · Accepted Answer · 2018-03-13 12:25:11Z

1

The long term solution to your problem is to define a custom class to be used as Data Transfer Object (DTO) where you cann access an items properties in a typesafe way:

class Item {
   private double id;
   private String name;
   public void setId(double id){this.id=id;}
   public double getId(){ return id;}
   public void setName(String name){this.name = name;}
   public String getName(){return name;}
}

usage:

for (int i = 0; i < items.size(); i++) {
    Item item = (LinkedTreeMap) items.get(i);

    // THIS LINE THROW EXCEPTION
    double d = item.getId();

    locations.put((int)item.getId(), item.getName());

answered Mar 13, 2018 at 12:25

Timothy Truckle

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