example of Java wildcard capture helper https://docs.oracle.com/javase/tutorial/java/generics/capture.html

Main.java

import java.util.ArrayList;
import java.util.List;

public class Main {

	public static void main(String[] args) {
		List<OutAndIn<?>> boo = new ArrayList<>();
		
		boo.add(new OutAndIn<String>("ffoo"));
		boo.add(new OutAndIn<Integer>(34));

		OutAndIn<?> outin = boo.get(0);
		// outin.printValue(outin.getValue()); // this is not allowed
		wildcardCapture(outin); // but this is
	}

	private static <E> void wildcardCapture(OutAndIn<E> outin) {
		outin.printValue(outin.getValue());
	}
}

OutAndIn.java

public class OutAndIn<E> {

	private E value;
	
	public OutAndIn(E value) {
		super();
		this.value = value;
	}

	public E getValue() {
		return value;
	}
	
	public void printValue(E value2) {
		System.out.println(value2);
	}

}