WorksheetsCollections
Total questions: 30
Worksheet time: 23mins
-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?
LinkedList
TreeMap
HashSet
LinkedHashMap
HashMap
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.
{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
{null=null, a=null, b=JavaSE, c=PHP, d=Python}
{a=null, b=JavaSE, c=PHP, d=Python}
{b=JavaSE, c=PHP, d=Python}
Compilation Fails
4
5
6
12
-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.
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
List listNames = new ArrayList();
listNames.add("Tom");
listNames.add("Mary");
listNames.add("Peter");
String name2 = (String) listNames.get(1);
System.out.println(name2);
What is the output of the above code
Tom
Mary
Peter
raises Exception
Which of the following statement is not True about Generics in java?
Generics are features of the Java programming language that allow programmers to write parameterized code.
With generics, the compiler can not detect violations at compile time, thus eliminating potential bugs.
Due to the demand of safer code, generics were added to the Java programming language.
generics allow you to write generic code
Stronger type checks at compile time
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
What is Collection in Java?
A group of objects
A group of classes
A group of interfaces
None of the mentioned
Which of these return type of hasNext() method of an iterator?
Integer
Double
Boolean
Collections Object
Which of these methods deletes all the elements from invoking collection?
clear();
reset();
delete();
remove();
Which of these interface declares core method that all collections will have?
Collection
EventListner
Comparator
Set
List
Which of these is static variable defined in Collections?
EMPTY_SET
EMPTY_LIST
EMPTY_MAP
All of the mentioned
What will be output of given code
a followed by concurrentModification Exception
a b c
a b
a c
Which interface does java.util.Hashtable implement?
Java.util.Map
Java.util.List
Java.util.HashTable
Java.util.Collection
You need to store elements in a collection that guarantees that no duplicates are stored and all elements can be accessed in natural order.
Which interface provides that capability?
java.util.Map
java.util.Set
java.util.List
java.util.Collection
Which collection class allows you to grow or shrink its size and provides indexed access to its elements, but whose methods are not synchronized?
java.util.HashSet
java.util.LinkedHashSet
java.util.List
java.util.ArrayList
What will be output of given code
1 2 3
1 followed by exception
Compile time error
run time error
Lists does not allow duplicates (True/False)
False
True
What is the advantage of Exception Handling
To avoid abnormal termination of a program
To find out errors
To Debug program
None of these
Which of the following key word is optional in Exception handling program
try
catch
finally
throw
try block may or may not contains catch blocks
True
False
Which of these keywords is not a part of exception handling?
try
finally
thrown
catch
java.lang.NullPointerException is a
Error
runtime exception
Compile time exception
None
Choose the CORRECT exception
String department="JTMK";
Integer no=Integer.parseInt(department);
ArithmeticException
NullPointerException
NumberFormatException
ArrayIndexOutOfBoundsException
Choose an exception if attempt to divide number by zero
int number = 89 / 0;
System.out.println("The answer is " + number);
ArithmeticException
NullPointerException
NumberFormatException
ArrayIndexOutOfBoundException
