Chapter 9 - Collections and Generics Flashcards
Comparable interface belongs in java.lang?
Yes
Comparator interface belong in java.lang?
No
Comparable does the ordering by multiples params?
No
Does the Comparable interface allow sorting of objects using only one natural ordering?
Yes
Can the Comparator interface be used to define multiple sorting orders for the same class?
Yes
Does implementing Comparable require overriding the compare() method?
No (Comparable requires overriding the compareTo() method, not compare())
Can a Comparator be passed to Java’s Collections.sort() method to change the sorting order?
Yes.
Is it mandatory for a class to implement Comparable to be sorted using a custom Comparator?
No
The List.of() method in Java 17 creates a mutable list.
False. List.of() creates an immutable list.
In Java 17, the HashSet class guarantees the order of elements.
False. HashSet does not guarantee any order of elements.
The Map.of() method in Java 17 can be used to create an immutable map with up to 10 key-value pairs.
Answer: True.
The Collections.emptyList() method returns a thread-safe, immutable empty list.
True.
Java 17’s TreeSet uses a Comparator for ordering elements if one is provided during construction.
True.
A collection is a group of objects contained in a single object.
If false, why?
True
The Java Collections Framework provides classes in java.util for storing and managing collections.
If false, why?
True
The List interface allows duplicate entries and provides ordered access to elements via an integer index.
If false, why?
True
A Queue orders its elements in a specific order for processing.
If false, why?
True
The diamond operator (<>) is a shorthand notation that reduces redundant generic type declarations.
If false, why?
True
The Set interface allows duplicate entries.
If false, why?
A Set does not allow duplicate entries.
(False)
A Deque is a subinterface of Map that allows access at both ends.
If false, why?
A Deque is a subinterface of Queue, not Map.
(False)
A Map allows duplicate keys.
If false, why?
A Map does not allow duplicate keys, only unique ones.
The diamond operator can be used in a variable declaration such as List<> list = new ArrayList<Integer>();.
If false, why?</Integer>
The diamond operator cannot be used in a variable declaration, only on the right side of an assignment.
The following method compiles: void use(List<> data) {}
If false, why? The diamond operator cannot be used in method parameters or type declarations.
(False)
The add() method inserts a new element into the Collection and returns whether it was successful.
True
The add() method in a Set always returns true.
(It returns false if the element already exists.)
The add() method in a List returns false when adding a duplicate element.
(Lists allow duplicates, so add() returns true.)
The remove() method removes a single matching value from the Collection and returns true if successful.
True
The remove() method removes all matching elements from the Collection.
(It removes only the first occurrence of a matching element.)
The isEmpty() method returns an int representing the number of elements.
(It returns a boolean.)
The size() method returns the number of elements in a Collection as an int.
True
The clear() method removes only null elements from the Collection.
(It removes all elements.)
The contains() method modifies the Collection if the value is present.
(It only checks for existence and does not modify the Collection.)
The removeIf() method takes a Consumer as an argument.
(It takes a Predicate.)
The forEach() method returns a value after processing all elements.
(It has a void return type.)
The forEach() method can only accept a lambda expression as an argument.
(It can also take a method reference.)
The removeIf() method removes all elements that match a given condition.
True
The contains() method checks whether an element is present using reference equality only.
(It checks using equals().)
