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Java SCJP Collection 1

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Java SCJP Collection 1
sonalihande81
Quiz by sonalihande81, updated more than 1 year ago
sonalihande81
Created by sonalihande81 over 9 years ago
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Resource summary

Question 1

Question
Which collection class(es) allows you to grow or shrink its size and provides indexed access to its elements, but whose methods are not synchronized? (Choose all that apply.)
Answer
  • java.util.HashSet
  • java.util.List
  • java.util.ArrayList
  • java.util.Vector
  • java.util.PriorityQueue
  • java.util.LinkedHashSet

Question 2

Question
Which one of the following is true about natual order and insertion order ?
Answer
  • insertion order means that the order in which the items are inserted into the collection
  • insertion order is determined by seeing if the element is inserted into the collection by using the insert() or add().
  • Natural order is different from insertion order is that the order incase of natural is determined by observing the data in the object in context
  • Natural order is not same as insertion order

Question 3

Question
Wchich implementation of Set would you choose if the you want the iterator of set would geive you objects in the order it were inserted ?
Answer
  • LinkedHashSet
  • TreeSet
  • HashSet

Question 4

Question
What is the data structure that a Set uses to store its elements ?
Answer
  • array
  • object
  • Map
  • ArrayList

Question 5

Question
Set allows at most one null element ?
Answer
  • True
  • False

Question 6

Question
If you were to use a List implementation,but not sure which one to, bacause the requirement is not yet clear. In this case which List implementation will you use ?
Answer
  • ArrayList
  • Vector
  • LinkedList

Question 7

Question
If you were to store objects into an implementation of List which happens only once in the entire lifecycle of the product,but reading these objects inside the List implementation is quite high,then which one would you use ?
Answer
  • Vector
  • LinkedList
  • ArrayList

Question 8

Question
Which of the following implementation will you use if you were to insert elements at any position in the collection ?
Answer
  • ArrayList
  • LinkedList
  • Vector

Question 9

Question
The EMPTY_LIST field and teh emptyList() method does return an empty immutable List .(The same also applies to EMPTY_SET,EMPTY_MAP and corresponding methods emptySet,emptyMap). Which of the following is/are true ?
Answer
  • There is no difference between the field and emptyList() ways to fetch an empty immutable list
  • The field gives you a non type-safe empty immutable object where are the method return type-safe empty immutable object of collection
  • The method to get the empty immutable collections are not static, so we need to create an object of Collections class in-order to call these methods,so fields like EMPTY_XXX are better choice if one doesn't want to create object of Collections.
  • The emptyXxx() methods actually returns the EMPTY_XXX fields.

Question 10

Question
Which of the following is true about creating an empty List, but immutable ?
Answer
  • final List immutableEmptyList=new ArrayList();
  • List immutableEmptyList=Collections.unmodifiableList(new List());
  • List immutableEmptyList=Collections.EMPTY_LIST
  • List immutableEmptyList=Collections.unmodifiableList(new ArrayList());

Question 11

Question
How do you get immutable object of a collection ? For example if you were to write an API which return a List or a Set or a Map when a method is called, but you also want that you don't want the client of your API to add or delete any object in the returned collection ?
Answer
  • Use Collections.immutableCollection() method.
  • Use the Collections.unmodifiableXxxx() method with the collection as an argument,which returns an immutable object of specific type.

Question 12

Question
Enumeration is an interface helps to iterate collection,but it can't remove any element the collection it is iterating
Answer
  • True
  • False

Question 13

Question
which of the following are false about Collections and Collection ?
Answer
  • Collections is a utility class
  • Collection is an interface to Set and List
  • Collections is a special type of collection which holds Set of collections
  • Both Collections and Collection entity belongs to java.util package.

Question 14

Question
Which of the following Collection are synchronized by nature ?
Answer
  • Vector
  • SortedSet
  • Hashtable
  • HashMap

Question 15

Question
Which of the following are true about ListIterator and Iterator ?
Answer
  • Iterator can traverse in forward direction only
  • ListIterator can traverse lists in both direction
  • Iterator can do operations like modifying the items it holds.
  • ListIterator extends the Iterator interface
  • Iterator can remove the elements
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