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How can I instantiate a type dynamically in Java

In my Java application, I have a method

public <T extends Transaction> boolean appendTransaction(T transaction) {
   ...
}

and inside this method I need to instantiate an object T that extends Transaction

Is it the right thing to do

T newTransaction = (T) transaction.getClass().newInstance();
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2 answers


I think you should use a factory -interface of type T, this way you can force create-instance on the user of the method.



public <T extends Transaction> boolean appendTransaction(
        T transaction, 
        Factory<T> factory) {
    ...
    T newTransaction = factory.createTransaction();
    ...
}
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More or less, except for what Class.newInstance

is evil:

Note that this method applies to any exception thrown by the nullable constructor, including the checked exception. Using this method effectively bypasses compile-time exception checking that would otherwise be performed by the compiler.



Use transaction.getClass().getConstructor().newInstance()

, it wraps exceptions thrown in the constructor with InvocationTargetException

.

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