Java Collections Proficiency (Advanced Level)

  • 26m
  • 26 questions
The Java Collections Proficiency (Advanced Level) benchmark measures your ability to use Java's built-in annotations, define and use custom annotations and classes, and use wildcards. A learner who scores high on this benchmark demonstrates that they have the skills to work with built-in and custom annotations, define generics, and use wildcards in Java.

Topics covered

  • analyze compiled bytecode to see how Java uses type erasure to ensure type safety and prevent code bloat
  • analyze how the @Deprecated annotation works on elements other than classes
  • apply default values to an element in annotation and also experiment with unnamed elements
  • apply the @Override annotation to detect typographical errors in method names at compile-time rather than at run-time
  • change the target policy to control exactly what code elements an annotation can be applied to
  • demonstrate that the @SafeVarargs annotation is purely indicative and does not perform any run-time or compile-time checks
  • describe how varargs are defined and used
  • describe the raw type underlying a generic type, and how if no type parameter is specified, Java makes the object of type java.lang.Object the type parameter
  • describe the use of custom annotations and recognize that these are usually purely intended to be understood by programmers and that the standard Java compiler does not understand them
  • describe the use of more than one type parameter
  • differentiate between bounded and unbounded type parameters
  • ensure that all the elements marked with an annotation satisfy certain conditions
  • enumerate different scenarios in which the @SuppressWarnings annotation can be applied
  • iterate over objects that have multiple type parameters
  • recognize different aspects of specifying and using type parameters
  • recognize different common overrides of methods in java.lang.Object such as the .toString, .equals, and .hashCode methods
  • recognize exactly what counts as a functional interface and what does not
  • recognize how annotations can be used with target policy Type_Use
  • recognize how the forRemoval named element from the @Deprecated annotation works
  • recognize how type parameters can be applied not only to classes, but also to specific methods inside classes
  • recognize how you can constrain type parameters to extend the Comparable and Serializable interfaces
  • recognize scenarios where capture errors might occur and some potential fixes for such capture errors
  • recognize the different warnings that can be eliminated using the @SuppressWarnings annotation, and why this annotation ought to be used sparingly, if at all
  • recognize use-cases where a base class specifies one type parameter and the derived class specifies multiple type parameters
  • use lower bounded wildcards to specify that a type parameter must be a super-class of a certain type
  • use upper bounded wildcards to specify that a type parameter must be a sub-class of a certain type