Java Programming - MCQ Practice Questions

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 will happen when you compile and run this code? java List<String> strings = Arrays.asList("a", "b", "c"); List raw = strings; raw.add(123); String s = strings.get(3);

Consider this declaration: public static <T> List<T> createList(). Which statement about type inference is correct?

What is the difference between List<Object> and List<?> in practical usage?

What is the compiled bytecode signature of this generic method? public <T extends Comparable<T>> T findMin(T[] arr)

Which statement about generic array creation is correct?

What output will this produce? java List<? super Integer> list = new ArrayList<Number>(); list.add(5); Integer val = (Integer) list.get(0);

Which Java feature was introduced specifically to support generics compilation?

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?

In a Spring Boot application, you need to create a generic repository interface that works with any entity type. Which declaration correctly implements this pattern?

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?

When using bounded type parameters with multiple interfaces, what is the correct syntax in Java?

A method processes collections where items need to be added back to the same collection type. Which wildcard approach ensures type safety for write operations?

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?