Java Programming - MCQ Practice Questions

Which statement correctly defines a generic class with multiple type parameters and bounds?

Consider: public static <T> T findMax(T a, T b) { return a; }. What is the issue with calling findMax(5, 3.5)?

What does List<?> represent in Java generics?

Which of the following will NOT compile?

Consider a generic interface: interface Comparable<T> { int compareTo(T obj); }. How should a class implement this for String comparison?

What happens when you use raw type List instead of List<String>?

What is the output? List<String> strings = new ArrayList<String>(); List list = strings; list.add(123); String str = strings.get(0); System.out.println(str);

How would you define a generic method that works with a pair of objects and returns the first one?

Consider the following code snippet: public <T> T processData(List<? extends T> list) { return list.get(0); } What is the relationship between the wildcard and type parameter T?

Which of the following will cause a compile-time error?

What does the following generic method signature indicate? public static <T extends Comparable<T>> T findMax(T[] array)

Given: Map<String, ? extends List<?>> map = new HashMap<>(); Which operation is valid?

What is the output of this code? List<String> strings = new ArrayList<>(); List raw = strings; raw.add(123); String str = strings.get(0);

Consider: public class Pair<T, U> { } Which declaration is invalid?

What is the correct way to declare a generic method that accepts a list and returns the maximum element?

Given the declaration: List<List<String>> listOfLists; Which assignment is valid?

What happens when you try to cast a generic object? List<String> strings = (List<String>) getSomeList();

In the context of generics, what does 'invariance' mean?

What does the following generic declaration mean? public <T extends Number & Comparable<T>> T findMax(T a, T b)

Consider the code: java List<Number> list = new ArrayList<Integer>(); Will this compile?