How can I instantiate a generic type in Java?

Question

I\'ve added a human-readable configuration file to my app using java.util.Properties and am trying to add a wrapper around it to make type conversions easier. Specifically,

Answer 1

Generics are implemented using type erasure in Java. In English terms, most generic information are lost at compile time, and you can't know the actual value of T at runtime. This means you simply can't instanciate generic types.

An alternate solution is to provide your class with the type at runtime:

class Test {

    Class klass;

    Test(Class klass) {
        this.klass = klass;
    }

    public void test() {
        klass.newInstance(); // With proper error handling
    }

}

Edit: New example closer to your case

static  T getProperty(String key, T fallback, Class klass) {
    // ...

    if (value == null) {
        return fallback;
    }
    return (T) klass.newInstance(); // With proper error handling
}