Java Programming - MCQ Practice Questions

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?

What is the correct output of this code? java List<? extends Number> list = new ArrayList<Integer>(); list.add(5);

Which wildcard usage follows the Producer pattern?

What does 'covariance' mean in the context of Java Generics?

What is the PECS principle in Java Generics?

Which of these is a valid generic interface implementation?

What is the runtime class object for this generic variable? java List<String> list = new ArrayList<String>(); Class<?> c = list.getClass();

A developer creates a generic method that accepts a collection of numbers and calculates their sum. Which type parameter declaration would be most appropriate for this scenario?

A utility class needs a method that accepts a List containing elements that are instances of a specific class or its subclasses. Which wildcard notation should be used?

In a microservices architecture, you're designing a Response wrapper class that should work with any data type, including primitives when boxed. Which implementation is correct?

Which of the following lambda expressions is invalid?

What is the type of the following lambda expression: x -> x.length()?

Which functional interface should be used for a lambda that filters elements?

What will this code print? List<Integer> list = Arrays.asList(1, 2, 3, 4, 5); list.forEach(x -> System.out.print(x + " "));

Can lambda expressions access local variables from their enclosing scope?

Which of the following correctly represents a BiFunction?