Java Test 19 – 2024

Welcome to your Java Test 19 - 2024

Name

Phone

Q1. Which of these statements concerning nested classes and interfaces are true?

You had to select 3 option(s)

An instance of a static nested class has an inherent outer instance.

A static nested class can contain non-static member variables.

A static nested interface can contain static member variables.

A static nested interface has an inherent outer instance associated with it.

For each instance of the outer class, there can exist many instances of a non-static inner class.

An inner class cannot have static members.

Q2. Identify correct statement(s) about Java records.

You had to select 2 option(s)

Records are implicitly final.

Records are implicitly static.

Records are meant to restrict the number of instances of that type.

Records are implicitly sealed.

Record instances are immutable.

Q3. You want to find out whether two strings are equal or not, in terms of the actual characters within the strings. What is the best way to do this?

You had to select 1 option(s)

use String's equals method.

use String's equalsIgnoreCase method.

Use == operator.

Use String's match method.

Use String's intern method.

None

Q4. Which of the following statements about starvation is correct?

You had to select 1 option(s)

Starvation occurs when threads become so busy in responding to each other that they are unable to perform any real work.

Starvation occurs when a thread is frequently unable to get access to a resource because the resource is hogged by other threads most of the time.

Starvation is a symptom of live lock in the threads.

Starvation is a symptom of deadlock in the threads.

None

Q5. Which of the following statements are true?

You had to select 3 option(s)

private keyword can never be applied to a class.

synchronized keyword can never be applied to a class.

synchronized keyword may be applied to a non-primitive variable.

final keyword can never be applied to a class.

A final variable can be hidden in a subclass.

sealed and non-sealed keywords can only be applied to classes and interfaces, not to enums and records.

Q6. Identify true statements about sealed classes.

You had to select 1 option(s)

A sealed class cannot be extended.

A sealed interface cannot be extended.

Only a class can be sealed and not an interface.

All reference types - classes, interfaces, enums, and records - can be marked as sealed.

None of the above.

None

Q7. The opening delimiter of a Java text block is:

You had to select 1 option(s)

"""

""" immediately followed by a new line

""" followed by any number of white spaces and then a new line

""" followed by one or more white spaces

None

Q8. What will the following code print?

void crazyLoop(){
var c = 0;
JACK: while (c < 8){
JILL: System.out.println(c);
if (c > 3) break JACK; else c++;
}
}

You had to select 1 option(s)

It will not compile.

It will throw an exception at runtime.

It will print numbers from 0 to 8

It will print numbers from 0 to 3

It will print numbers from 0 to 4

None

Q9. Given the following code:

abstract class Device{
String name;
String number;
String address;
int frequency;

abstract void setName(String name);
abstract void connect();
abstract void disconnect();
abstract void call(String number);
abstract void listenOn(int frequency);

}

interface Caller{ }

interface Receiver{ }

class Phone extends Device implements Caller{ }
class TV extends Device implements Receiver{ }
class WalkieTalkie extends Device implements Caller, Receiver{ }

and the following requirements specification regarding the call and listenOn functionality:

1. Phone supports only the call operation. Users should have the ability to call a number, but not set the frequencey. Assume frequency is fixed at 0.

2. TV supports only the listenOn operation. Users should have the ability to set the frequency using the listenOn method, but not change the number. Assume number is fixed at "0".

3. WalkieTalkie contains both call and listenOn features. Users should have the ability to call a number using call as well as set frequency using listenOn.

The methods setName, connect, and disconnect are applicable to Phone, TV, and WalkieTalkie.

Which two changes together would allow you to achieve these specifications?

You had to select 2 option(s)

make Device an interface rather than an abstract class

move String number from Device to Caller

move int frequency from Device to Receiver

make Device, rather than Phone, TV, and WalkieTalkie implement Caller and Receiver.

move call from Device to Caller

move listenOn from Device to Receiver

Q10. Which is/are the root interface(s) for all collection related interfaces?

You had to select 2 option(s)

BaseCollection

Collection

List

Set

Map

Q11. Which of the following are NOT valid operators in Java?

You had to select 4 option(s)

sizeof

<<<

instanceof

mod

equals

Q12. Using a Callable would be more appropriate than using a Runnable in which of the following situations?

You had to select 1 option(s)

When you want to execute a task directly in a separate thread.

When your task might throw a checked exception and you want to execute it in a separate Thread.

When your task does not return any result but you want to execute the task asynchronously.

When you want to use ExecutorService to submit multiple instances of a task.

None

Q13. Which of the following command line switches is required (independent of each other) to run a modular application stored in c:\modules\movies.jar?

You had to select 3 option(s)

-m c:\modules\movies.jar

-p c:\modules\movies.jar

-p c:\modules

--path c:\modules\movies.jar

--module-path c:\modules

Q14. Given:

//In file AccessTest.java
package a;
public class AccessTest {
int a;
private int b;
protected void c(){ }
public int d(){ return 0; }
}

//In file AccessTester.java
package b;
import a.AccessTest;

public class AccessTester extends AccessTest{
public static void main(String[] args) {
AccessTest ref = new AccessTest();

}
}

Identify the correct statements -

You had to select 1 option(s)

Only c() and d() can be accessed by ref.

b, c(), as well as d(), can be accessed by ref.

Only d() can be accessed by ref.

Only a and d() can be accessed by ref.

None

Q15. Which of the following is/are valid functional interfaces?

You had to select 1 option(s)

interface F{
default void m(){ }
}

interface F{
default void m(){ }
static void n(){ }
}

interface F{
void m();
void n();
}

interface F{
default void m(){ }
abstract void n();
}

interface F{
void m(){ }
}

None

Q16. Under what situations does a class get a default constructor?

You had to select 1 option(s)

All classes in Java get a default constructor.

You have to define at least one constructor to get the default constructor.

If the class does not define any constructors explicitly.

All classes get default constructor from Object class.

None of the above.

None

Q17. Where, in a constructor, can you place a call to a super class's constructor ?

You had to select 1 option(s)

Anywhere in the constructor's body.

As the first statement in the constructor.

Only as the first statement and it can be called just like any other method call i.e. ClassName( ... ).

You can't call super class's constructor in a base class as constructors are not inherited.

None of the above.

None

Q18. Consider the following code:

Locale myLoc = new Locale("fr", "FR");
ResourceBundle rb = ResourceBundle.getBundle("appmessages", myLoc);
//INSERT CODE HERE

Which of the following lines of code will assign a ResourceBundle for a different Locale to rb than the one currently assigned?

You had to select 2 option(s)

rb = ResourceBundle.getBundle("appmessages", new Locale("ch", "CH"));

rb = ResourceBundle.getBundle("appmessages", CHINA);

myLoc.setLocale(Locale.CHINA);

myLoc.setLocale(new Locale("ch", "CH"));

rb = ResourceBundle.getBundle("appmessages", Locale.CHINA);

rb.setLocale(Locale.CHINA);

Q19. Which of the following are true about the enhanced for loop?

You had to select 3 option(s)

It can iterate over an array or a Collection but not a Map.

Using an enhanced for loop prevents the code from going into an infinite loop.

Using an enhanced for loop on an array may cause infinite loop.

An enhanced for loop can iterate over a Map.

You cannot find out the number of the current iteration while iterating.

var declaration cannot be used for declaring the loop variable.

Q20. Which of the following method(s) of java.util.stream.Stream interface is/are used for reduction?

You had to select 2 option(s)

filter

reduce

sum

max

add

Q21. Given the following declaration, select the correct way to get the number of elements in the array, assuming that the array has been initialized.

int[] intArr;

You had to select 1 option(s)

intArr[ ].length( )

intArr.length( )

intArr.length

intArr[ ].size( )

intArr.size( )

None

Q22. Which of the following can be used as a constructor for the class given below?

public class TestClass{
final int a;
// lots of irrelevant code
}

You had to select 1 option(s)

public void TestClass() { a = 10; }

public TestClass() { }

public static TestClass(int param) { a = param; }

public final TestClass() { a = 10; }

public TestClass(int x) { a = x; }

public TestClass() { System.out.println(a); }

public TestClass(int x) { System.out.println(a); a = x; }

None

Q23. A method with no access modifier defined in a class can be overridden by a method marked protected (assuming that it is not final) in the sub class.

You had to select 1 option(s)

True

False

None

Q24. Given that daylight Savings Time ends on Nov 6 at 2 AM in US/Eastern time zone. (As a result, 2 AM becomes 1 AM. In other words, one minute after 1.59 AM, the clock shows 1 AM instead of 2 AM.), what will the following code print?

LocalDateTime ld = LocalDateTime.of(2022, Month.NOVEMBER, 6, 1, 30);
ZonedDateTime date1 = ZonedDateTime.of(ld, ZoneId.of("US/Eastern"));
ZonedDateTime date2 = date1.plusHours(1);
System.out.println(date1.getHour()+" "+date2.getHour());

You had to select 1 option(s)

-1 -1

-1 -2

1 2

1 1

2 1

None

Q25. Which of the following tools support the --show-module-resolution option?

You had to select 1 option(s)

java

javac

jar

jmod

jdeps

None

Q26. Identify legal module names.

You had to select 3 option(s)

com.amazing.movie-rentals

com.amazing.movierentals

amazing-movierentals

com.amazing.$movierentals

no1movierentals

com.amazing.1movierentals

Q27. Given the following definition of class, which member variables are accessible from OUTSIDE the package com.enthu.qb?

package com.enthu.qb;
public class TestClass{
int i;
public int j;
protected int k;
private int l;
}

You had to select 2 option(s)

Member variable i.

Member variable j.

Member variable k.

Member variable k, but only for subclasses.

Member variable l.

Q28. Identify examples of auto-unboxing.

You had to select 2 option(s)

Q29. Which of the following code fragments will you use to create an ExecutorService?

You had to select 2 option(s)

ExecutorService

Executor

Executors

.newSingleThreadExecutor();

.createSingleThreadExecutor();

.getSingleThreadExecutor();

Q30. Identify the correct statement about i18n.

You had to select 2 option(s)

I18N class allows you to port your code for multiple regions and/or languages.

You should use Locale and formatter objects such as NumberFormat and DateFormat to generate locale specific output.

The i18n method of NumberFormat and DateFormat allows you to generate locale specific output.

Using default locale for NumberFormat and DateFormat automatically ensures that the formatted text will be localized to the location setting of the machine on which the code is run.
(Assuming that default locale hasn't been explicitly changed by any means.)

i18n stands for Internationalization and it is handled automatically by Java.

Q31. The following code snippet will print 'true'.

short s = Short.MAX_VALUE;
char c = s;
System.out.println( c == Short.MAX_VALUE);

You had to select 1 option(s)

True

False

None

Q32. Which of the following statements are true?

You had to select 2 option(s)

A nested class may be declared static.

Anonymous inner class may be declared public.

Anonymous inner class may be declared private.

Anonymous inner class may be declared protected.

Anonymous inner class may extend an abstract class.

Q33. The signature of a method in a class is as follows:

public static List doIt(List nums)

This method is being called in the following code:

result = doIt(in);

Given that String implements CharSequence interface, what should be the reference type of in and result variables?

You had to select 1 option(s)

None of these.

None

Q34. Which of these methods are defined in the Map interface?

You had to select 2 option(s)

contains(Object o)

addAll(Collection c)

remove(Object o)

values( )

toArray( )

Q35. Objects of which of the following classes can be thrown using a throw statement?

You had to select 3 option(s)

Event

Object

Throwable

Exception

RuntimeException

Q36. Consider the following method :

public void myMethod(int m, Object p, double d){
... valid code here
}

Assuming that there is no other method with the same name, which of the following options are correct regarding the above method?

You had to select 1 option(s)

If this method is called with two parameters, the value of d in the method will be 0.0.

If this method is called with one parameter, the value of p and d in the method will be null and 0.0 respectively.

If this method is called with one parameter, the call will throw a NullPointerException.

If this method is called with one parameter, the call will throw a NullPointerException only if the code in the method tries to access p.

If this method is called with two parameters, the code will not compile.

None

Q37. Identify correct statement(s) about switch expressions written using the new arrow syntax.

You had to select 3 option(s)

Every case block must either have a yield or a break.

Every case must either have a case expression or a case block.

Every case must return a value or throw an exception.

A switch expression must end with a semi-colon.

Q38. What is meant by "encapsulation" ?

You had to select 1 option(s)

There is no way to access member variable.

There are no member variables.

Member fields are declared private and public accessor/mutator methods are provided to access and change their values if needed.

Data fields are declared public and accessor methods are provided to access and change their values.

None

Q39. Which of the following method calls can be applied to a String object?

You had to select 5 option(s)

repeat(int )

equalsIgnoreCase(String)

prune()

append()

intern()

compareTo(String )

transform(Function< ? super String,? extends R > f)

Q40. Complete the following code by inserting declaration for stateCitiesMap:

//Insert line of code here

List cities = new ArrayList();
cities.add("New York");
cities.add("Albany");
stateCitiesMap.put("NY", cities);

You had to select 2 option(s)

Q41. Which of the following are correct about java.util.function.Predicate?

You had to select 1 option(s)

It is an interface that has only one abstract method (among other non-abstract methods) with the signature -
public void test(T t);

It is an interface that has only one abstract method (among other non-abstract methods) with the signature -
public boolean test(T t);

It is an abstract class that has only one abstract method (among other non-abstract methods) with the signature -
public abstract void test(T t);

It is an abstract class that has only one abstract method (among other non-abstract methods) with the signature -
public abstract boolean test(T t);

None

Q42. Your application needs to load a set of key value pairs from a database table which never changes. Multiple threads need to access this information but none of them changes it.

Which class would be the most appropriate to store such data if the values need not be kept in a sorted fashion?

You had to select 1 option(s)

Hashtable

HashMap

Set

TreeMap

List

None

Q43. Which of these statements are true?

You had to select 2 option(s)

A static method can call other non-static methods in the same class by using the 'this' keyword.

A class may contain both static and non-static variables and both static and non-static methods.

Each object of a class has its own copy of each non-static member variable.

Instance methods may access local variables of static methods.

All methods in a class are implicitly passed a 'this' parameter when called.

Q44. A JDBC driver implementation must provide implementation classes for which of the following interfaces?

You had to select 3 option(s)

java.sql.DriverManager

java.sql.Driver

java.sql.Connection

java.sql.Statement

java.sql.SQLException

java.sql.Date

Q45. You have a collection (say, an ArrayList) which is read by multiple reader threads and which is modified by a single writer thread. The collection allows multiple concurrent reads but does not tolerate concurrent read and write. Which of the following strategies will you use to obtain best performance?

You had to select 1 option(s)

synchronize all access to the collection.

make the collection variable final.

make the collection variable final and volatile.

Wrap the collection into its synchronized version using Collections.synchronizedCollection().

Encapsulate the collection into another class and use ReadWriteLock to manage read and write access.

None

Q46. Which of these implementations for collection framework interfaces are provided in the standard JDK?

You had to select 3 option(s)

TreeMap

ArrayMap

HashSet

ArrayList

Q47. Given that TestClass is a class, how many objects and reference variables are created by the following code?

TestClass t1, t2, t3, t4;
t1 = t2 = new TestClass();
t3 = new TestClass();

You had to select 1 option(s)

2 objects, 3 references.

2 objects, 4 references.

3 objects, 2 references.

2 objects, 2 references.

None of the above.

None

Q48. You are implementing a special sorting algorithm that can sort objects of different classes. Which of the following class declarations will you use?

You had to select 1 option(s)

public class SpecialSorter<>{
...
}

public class SpecialSorter< K >{
...
}

public class <SpecialSorter>{
...
}

public class SpecialSorter(K){
...
}

None

Q49. Which of the following are true regarding the Date-Time API of java.time package?

You had to select 2 option(s)

It uses the calendar system defined in ISO-8601 as the default calendar.

Most of the actual date related classes in the Date-Time API such as LocalDate, LocalTime, and LocalDateTime are immutable.

LocalDateTime includes time zone information but LocalDate does not.

To create a LocalDate or a LocalDateTime object, you can use one of their several constructors.

Q50. Which of the following code fragments can you use to get a JDBC connection?

You had to select 1 option(s)

Properties p = new Properties();
  p.setProperty("user", userid);
  p.setProperty("password", pwd);
  DriverManager.setClientInfo(p);
  Connection c = DriverManager.getConnection(url);

Properties p = new Properties();
  p.setProperty("user", userid);
  p.setProperty("password", pwd);
  Connection c = DriverManager.getConnection(dburl);
  c.setClientInfo(p);
  c.connect();

Properties p = new Properties();
  p.setProperty(''user'', userid);
  p.setProperty(''password'', pwd);
  Connection c =  DriverManager.getConnection(dburl, p);

Connection c = DriverManager.getConnection(url);
c.connect(userid, pwd)

None

Q51. What classes can a non-static nested class extend ?

(Provided that the class to be extended is visible and is not final.)

You had to select 1 option(s)

Only the encapsulating class.

Any top level class.

Any class.

It depends on whether the inner class is defined in a method or not.

None of the above.

None

Q52. Which of the following statements are correct?

You had to select 3 option(s)

An abstract class can be extended by an abstract or a concrete class.

A concrete class can be extended by an abstract or a concrete class.

An interface can be extended by another interface.

An interface can be extended by an abstract class.

An interface can be extended by a concrete class.

An abstract class cannot implement an interface.

Q53. What class of objects can be declared by the throws clause?

You had to select 3 option(s)

Exception

Error

Event

Object

RuntimeException

Q54. Compared to public, protected, and private accessibilities, default accessibility is....

You had to select 1 option(s)

Less restrictive than public.

More restrictive than public, but less restrictive than protected.

More restrictive than protected, but less restrictive than private.

More restrictive than private.

Less restrictive than protected from within a package, and more restrictive than protected from outside a package.

None

Q55. Which of the following statements are true?

You had to select 3 option(s)

Non-static nested classes must have either default or public accessibility.

Non-static nested classes cannot contain static members.

Methods in all nested classes can be declared static.

All nested classes can be declared static.

A static nested class can contain a non - static inner class.

A nested class may be sealed.

Time's up

Time is Up!

Java Test 19 – 2024

Q1. Which of these statements concerning nested classes and interfaces are true?

Q2. Identify correct statement(s) about Java records.

Q3. You want to find out whether two strings are equal or not, in terms of the actual characters within the strings. What is the best way to do this?

Q4. Which of the following statements about starvation is correct?

Q5. Which of the following statements are true?

Q6. Identify true statements about sealed classes.

Q7. The opening delimiter of a Java text block is:

Q8. What will the following code print?

Q9. Given the following code:

Q10. Which is/are the root interface(s) for all collection related interfaces?

Q11. Which of the following are NOT valid operators in Java?

Q12. Using a Callable would be more appropriate than using a Runnable in which of the following situations?

Q13. Which of the following command line switches is required (independent of each other) to run a modular application stored in c:\modules\movies.jar?

Q14. Given:

Q15. Which of the following is/are valid functional interfaces?

Q16. Under what situations does a class get a default constructor?

Q17. Where, in a constructor, can you place a call to a super class's constructor ?

Q18. Consider the following code:

Q19. Which of the following are true about the enhanced for loop?

Q20. Which of the following method(s) of java.util.stream.Stream interface is/are used for reduction?

Q21. Given the following declaration, select the correct way to get the number of elements in the array, assuming that the array has been initialized.

Q22. Which of the following can be used as a constructor for the class given below?

Q23. A method with no access modifier defined in a class can be overridden by a method marked protected (assuming that it is not final) in the sub class.

Q24. Given that daylight Savings Time ends on Nov 6 at 2 AM in US/Eastern time zone. (As a result, 2 AM becomes 1 AM. In other words, one minute after 1.59 AM, the clock shows 1 AM instead of 2 AM.), what will the following code print?

Q25. Which of the following tools support the --show-module-resolution option?

Q26. Identify legal module names.

Q27. Given the following definition of class, which member variables are accessible from OUTSIDE the package com.enthu.qb?

Q28. Identify examples of auto-unboxing.

Q29. Which of the following code fragments will you use to create an ExecutorService?

Q30. Identify the correct statement about i18n.

Q31. The following code snippet will print 'true'.

Q32. Which of the following statements are true?

Q33. The signature of a method in a class is as follows:

Q34. Which of these methods are defined in the Map interface?

Q35. Objects of which of the following classes can be thrown using a throw statement?

Q36. Consider the following method :

Q37. Identify correct statement(s) about switch expressions written using the new arrow syntax.

Q38. What is meant by "encapsulation" ?

Q39. Which of the following method calls can be applied to a String object?

Q40. Complete the following code by inserting declaration for stateCitiesMap:

Q41. Which of the following are correct about java.util.function.Predicate?

Q42. Your application needs to load a set of key value pairs from a database table which never changes. Multiple threads need to access this information but none of them changes it.

Which class would be the most appropriate to store such data if the values need not be kept in a sorted fashion?

Q43. Which of these statements are true?

Q44. A JDBC driver implementation must provide implementation classes for which of the following interfaces?

Q46. Which of these implementations for collection framework interfaces are provided in the standard JDK?

Q47. Given that TestClass is a class, how many objects and reference variables are created by the following code?

Q48. You are implementing a special sorting algorithm that can sort objects of different classes. Which of the following class declarations will you use?

Q49. Which of the following are true regarding the Date-Time API of java.time package?

Q50. Which of the following code fragments can you use to get a JDBC connection?

Q51. What classes can a non-static nested class extend ?

Q52. Which of the following statements are correct?

Q53. What class of objects can be declared by the throws clause?

Q54. Compared to public, protected, and private accessibilities, default accessibility is....

Q55. Which of the following statements are true?

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