How to Determine the Class of a Generic Type in Generic Classes?

Generic Type Class Determination in Generic Classes

In object-oriented programming, determining the class of a generic type is often necessary. However, when using generic classes, this task becomes challenging due to type erasure at runtime.

Consider the following example where the MyGenericClass attempts to create an instance of type T using a third-party library:

public class MyGenericClass<T> {
  public void doSomething() {
    // Create an instance of class T
    T bean = (T)someObject.create(T.class);
  }
}

This approach fails with an "Illegal class literal for the type parameter T" error. To address this issue, a common workaround is to pass the type T as a parameter to a static method:

public class MyGenericClass<T> {

    private final Class<T> clazz;

    public static <U> MyGenericClass<U> createMyGeneric(Class<U> clazz) {
        return new MyGenericClass<U>(clazz);
    }

    protected MyGenericClass(Class<T> clazz) {
        this.clazz = clazz;
    }

    public void doSomething() {
        // Create an instance of class T
        T instance = clazz.newInstance();
    }
}

By passing the class T explicitly, the code can successfully create an instance of the desired type. Although this method is not as elegant as a direct method call, it provides a reliable solution for determining the class of a generic type.

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