How do I find out what type each object is in a ArrayList<Object>?

java generics reflection arraylist
WolfmanDragon picture WolfmanDragon · Sep 20, 2008 · Viewed 265.7k times · Source

I have a ArrayList made up of different elements imported from a db, made up of strings, numbers, doubles and ints. Is there a way to use a reflection type technique to find out what each type of data each element holds?

FYI: The reason that there is so many types of data is that this is a piece of java code being written to be implemented with different DB's.

Answer

Frank Krueger picture Frank Krueger · Sep 20, 2008

In C#:
Fixed with recommendation from Mike

ArrayList list = ...;
// List<object> list = ...;
foreach (object o in list) {
    if (o is int) {
        HandleInt((int)o);
    }
    else if (o is string) {
        HandleString((string)o);
    }
    ...
}

In Java:

ArrayList<Object> list = ...;
for (Object o : list) {
    if (o instanceof Integer)) {
        handleInt((Integer o).intValue());
    }
    else if (o instanceof String)) {
        handleString((String)o);
    }
    ...
}

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