How to use Java class type in code

Question

I've used and extended classes where the name looks like ArrayAdapter<String> or HashMap<String, String>, but how can implement the type inside the <> myself? For example, I have a class that is currently used to store callback data. It looks like:

static class APICallback {
    boolean status;
    JsonObject data;
}

Is there a way for me to implement this so that I can code something like APICallback<List<String>> and have it know the data field will be a List<String> vs a JsonObject?

docs.oracle.com/javase/tutorial/java/generics

badfilms
– badfilms

2015-03-09 01:12:02 +00:00
Commented Mar 9, 2015 at 1:12 — badfilms
– badfilms, Commented Mar 9, 2015 at 1:12

mkobit · Accepted Answer · 2015-03-09 01:11:45Z

3

Your class would have to be a generic type:

E.g:

static class APICallback<T> {
    boolean status;
    T data;
}

answered Mar 9, 2015 at 1:11

mkobit

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Comments

Elliott Frisch · Accepted Answer · 2015-03-09 01:12:15Z

2

If I understand your question, you want to know about generic types (from the link) a generic type is a generic class or interface that is parameterized over types. One possible way to make your class generic would be

static class APICallback<T> {
    boolean status;
    JsonObject data;
    List<T> al;
}

answered Mar 9, 2015 at 1:12

Elliott Frisch

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