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Java - What is difference between List<?> and List<Object>?
1 answers
6 points
As in the question.
I am thinking what is difference between List<?> and List<Object>?
Each class extends Object, so why it was introduced?
1 answer
6 points
By using List<?> you are able to assign to variable types of:
List<String>,List<Integer>,List<Boolean>,List<Object>,- etc.
By using List<Object> you are not.
Example source code:
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import java.util.List;2
import java.util.ArrayList;3
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public class Program {5
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public static void main(String[] args) {7
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List<?> a = new ArrayList<String>();9
List<?> b = new ArrayList<Integer>();10
List<?> c = new ArrayList<Boolean>();11
List<?> d = new ArrayList<Object>();12
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// List<Object> a = new ArrayList<String>(); // <--- incorrect assignment14
// List<Object> b = new ArrayList<Integer>(); // <--- incorrect assignment15
// List<Object> c = new ArrayList<Boolean>(); // <--- incorrect assignment16
// List<Object> d = new ArrayList<Object>(); // <--- incorrect assignment17
}18
}
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