Java Practice Quiz

Which of these classes provides the specified features?

-Contains no duplicate elements.

-Can contain at most one Null value.

-Elements are not key-value pairs.

-Accessing an element can be almost as fast as performing a similar operation on an array.

• LinkedList

• TreeMap

• HashSet

• LinkedHashMap

• HashMap

Which of these interface is not part of Java’s collection framework?

• List

• Sorted List

• Set

• Sorted Map

Which of these return type of hasNext() method of an iterator?

• Integer

• Double

• Boolean

• Collections Object

Which of the following statement about Set is true?

• A HashSet cannot have a null value.

• Set allows duplicate values.

• Set allows null values but only single occurrence.

• Set extends the Java.util.collection interface.

-Entries are organized as key/value pairs.

-Duplicate entries replace old entries.

-Entries are sorted using a Comparator or the Comparable interface.

Which interface of the java.util package offers the specified behavior?

• List

• Map

• Set

• SortedSet

• SortedMap

• {1=C, 2=JavaEE, 4=Python, 3=PHP}

• {1=C, 2=JavaSE, 3=Python, 4=PHP}

• {1=C, 2=JavaEE, 3=Python, 4=PHP}

• {1=C, 2=JavaSE,2=JavaEE, 3=Python, 4=PHP}

• NullPointerException

-Entries are not organized as key/value pairs.

-Duplicate entries are rejected.

Which interface of the java.util package offers the specified behavior?

• List

• Map

• Set

• None of the above

Which of the following is/are correct statements?

• HashSet class implements the Set interface

• HashSet does not allow duplicate elements that means you can not store duplicate values in HashSet.

• HashSet permits to have a single null value.

• HashMap does not allow duplicate keys however it allows to have duplicate values.

• HashMap and HashSet are threadsafe

• {"Computer", "Programming","Networks","null"}

• {"Computer", "Programming","Networks",null,"null"}

• Line 11 : Genetates NullPointer Exception

• Line12: Generates NullPointerException

Which of the following statement(s) is/are FALSE?

• TreeSet does not preserve the insertion order of elements but elements are sorted by keys.

• Objects in a TreeSet are stored in a sorted and ascending order.

• TreeSet does not allow to insert Heterogeneous objects. It will throw classCastException at Runtime if trying to add hetrogeneous objects.

• Comparator is note provided for TreeSet.