Java T initialize

Question

How to create class of T?

I need to bind from some Windows Communication Foundation (WCF) XML of the object T.

I can do this without errors:

ArrayList<T> list = new ArrayList<T>();

This is my function:

public static <T> ArrayList<T> GetListFromXml(String url,String element)

How to get: T obj = ?

Did you work through the [Java Generics tutorial](http://docs.oracle.com/javase/tutorial/java/generics/)? — , Mar 02 '12 at 09:18

Arne Burmeister · Accepted Answer · 2012-03-05T07:55:07.767

3

That is not possible due to the type erasure of the compiler. If you have a concrete type with a default constructor on caller side, the following may work:

public static <T> ArrayList<T> GetListFromXml(String url,String element, Class<? extends T> type) {
  T obj = type.newInstance();
  ...
}

If you need to pass parameters to the constructor, you have to get it from the class by getConstructor(parameter type 1, ...) (you need to handle the Exceptions not shown here):

MyParamType1 param1 = ...;
MyParamType2 param2 = ...;
Constructor<T> cons = type.getConstructor(MyParamType1.class, MyParamType2.class);
T obj = const.newInstance(param1, param2);

edited Mar 05 '12 at 07:55

answered Mar 01 '12 at 15:10

Arne Burmeister

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`ArrayList ycList = GetListFromXml(url, element, YourClass.class);`. [Class literals](http://stackoverflow.com/questions/2160788/what-is-a-class-literal-in-java). – Mersenne Mar 01 '12 at 15:30
can i send prameters to the constractor? – roy.d Mar 01 '12 at 15:44
@user1194088 You can send the type as a parameter to a class which takes a parameter e.g. if you write one. ArrayList doesn't take a type. – Peter Lawrey Mar 01 '12 at 15:47
i meant sent prameters to the T constractor, – roy.d Mar 04 '12 at 06:51

Java T initialize

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