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Bazując na świetnej podpowiedzi Guadalupe Gagnon proponuję: 1. Zamiast ogólnego parametru T dać String 2. W klasie StringObject zaimplementować metodę z interfejsu SimpleObject 3. Zwrócić jako wartość realizację metody SimpleObject, to już jest proste (dotyczy drugiego członu metody).

Its been awhile since I did this task, but here are a few things to consider: #1 This is the definition of a parameterized interface.

interface SimpleObject<T> {
   SimpleObject<T> getInstance
}

The letter 'T' in this code is a generic and this letter can be any letter you want, though T is commonly used (like 'i' is used in for loops) and stands for 'Type'. When using this definition in code you would replace the 'T' with the type that you want, such as String, int, char, or any that you need. #2 The method on line 16 is actually really close to being correct, you just need to make sure that it follows the definition that the interface spells out. a) It should not have any arguments; and b) it needs to return an instance of SimpleObject of the correct 'Type' that the conditions say. You have been using parameterized classes a lot already. To give you an example, the ArrayList class is defined (in simple terms) as

class ArrayList implements List<T> {
   // all the other code
}

and in code you would create an array list such as:

ArrayList<Integer> iList = new ArrayList<>();  // for an Integer ArrayList
ArrayList<Short> slist = new ArrayList<>();  // for a Short ArrayList

#3 Remember that interfaces can not be instantiated by just calling new Interface(), they can only be instantiated by calling the new ClassThatImplementsInterface(). Figure out these 3 points and you should easily pass this task.