Java Collections (Map, Set)

-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.

Which of these classes provides the specified features?

• ArrayList

• TreeMap

• HashSet

• LinkedHashMap

• HashMap

Which of the following statement about Set is true?

• A Set is a class so you can say new Set()

• Set allows duplicate values.

• Sets are always ordered least to greatest

• 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

• TreeSet

• TreeMap

• {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

• [Computer, Network, Networks, Programming, Security]

• [Computer, Programming, Network, Networks, Programming, Security]

• [Computer, Programming, Computer, Networks, Network, Security]

• [Computer, Networks, Network, Programming, Security]

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.

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

Which of the following is/ are True ?

• Set is a group of ordered objects without duplicates

• Map is essentially a set of (key,value) pairs with unique keys, supporting a lookup operation to find the value associated with a given key

• List is a sequence of objects, with a distinguished first object, and in which each object has a unique successor.

When do we use sets in java program?

• To allow null and duplicate elements

• You want to store elements distinctly without duplication, or unique elements.

• to allow t contain duplicate keys and each key can map to at most one value

• To perform lookups by keys

What will happen if an element already present in the Set is added again?

• Run time error will be generated

• No error, the element will be added once again to the set

• Compile time error

• A boolean value of false will be returned, and the value will not be added to the Set