Java Test 17 – Java SE 21 practice tests

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Welcome to your Foundation Test 1 - 2025

Name

Phone

Q1. Consider the following code:

public static void main(String[] args) {
int[] values = { 10, 30, 50 };
for( var val : values ){
var x = 0;
while(x<values.length){
System.out.println(x+" "+val);
x++;
}
}
}

How many times is 2 printed out in the output?

Select 1 option(s)

None

Q2. Which method must be implemented by a class implementing the Callable interface?

Select 1 option(s)

run()

execute()

call()

do()

None

Q3. Consider the following code:

public abstract class TestClass{
public abstract void m1();

public abstract void m2(){
System.out.println("hello");
}
}

Which of the following corrections can be applied to the above code (independently) so that it compiles without any error?

Select 2 option(s)

Replace the method body of m2() with a ; (semi-colon).

Replace the ; at the end of m1() with a method body.

Remove abstract from m2().

Remove abstract from the class declaration.

Q4. What will the following code print?

System.out.println("12345".charAt(6));

Select 1 option(s)

null

-1

It will throw an ArrayIndexOutOfBoundsException.

It will throw a StringOutOfBoundsException.

It will throw an IndexOutOfBoundsException

None

Q5. Which statements concerning conversion are true?

Select 4 option(s)

Conversion from char to long does not need a cast.

Conversion from byte to short does not need a cast.

Conversion from short to char needs a cast.

Conversion from int to float needs a cast.

Conversion from byte, char or short to int, long, or float does not need a cast.

Q6. In which of the following cases can the Console object be acquired?

Select 1 option(s)

When the JVM is started from an interactive command line with explicitly redirecting the standard input and output streams to Console.

When the JVM is started from an interactive command line without redirecting the standard input and output streams.

When the JVM is started in the background with the standard input and output streams directed to Console.

When the JVM is started in the background without redirecting the standard input and output streams.

None

Q7. Given the following line of code:

List students = new ArrayList();

Identify the correct statement:

Select 1 option(s)

The reference type is List and the object type is ArrayList.

The reference type is ArrayList and the object type is ArrayList.

The reference type is ArrayList and the object type is List.

The reference type is List and the object type is List.

None

Q8. How can you declare a method someMethod() such that an instance of the class is not needed to access it and all the members of the same package have access to it.

Select 3 option(s)

public static void someMethod()

static void someMethod()

protected static void someMethod()

void someMethod()

protected void someMethod()

public abstract static void someMethod()

Q9. Which of the following statements are correct regarding a functional interface?

Select 1 option(s)

It has exactly one method and it must be abstract.

It has exactly one method and it may or may not be abstract.

It must have exactly one abstract method and may have other default or static methods.

It must have exactly one static method and may have other default or abstract methods.

None

Q10. Which of the following statements regarding break and continue are true?

Select 1 option(s)

break without a label can occur only in a switch, while, do, or for statement.

continue without a label can occur only in a switch, while, do, or for statement.

break can never occur without a label.

continue can never occur WITH a label.

None of the above.

None

Q11. Which of the following classes are thread safe?

Select 2 option(s)

java.util.Date

java.time.Instant

java.util.Calendar

java.util.GregorianCalendar

java.time.Duration

Q12. Which of these statements about interfaces are true?

Select 4 option(s)

Interfaces are always abstract.

An interface can have static methods.

All methods in an interface are abstract although you need not declare them to be so.

Fields of an interface may be declared as transient or volatile but not synchronized.

Interfaces cannot be final.

Interfaces allow multiple implementation inheritance through default methods.

Q13. Which of the following are required to construct a Locale?

Select 1 option(s)

language

region

country

time zone

state

culture

None

Q14. Which of the following are valid?

Select 2 option(s)

List< String > list = new List< >();

ArrayList< String > list = new List< >();

ArrayList< > list = new ArrayList< >();

List< String > list = new ArrayList< >();

List< String > list = new ArrayList< >(10);

Q15. Which of these are NOT part of the StringBuilder class?

Select 1 option(s)

trim( )

ensureCapacity(int )

append(boolean)

reverse( )

setLength(int)

compareTo

None

Q16. Which of these statements are true?

Select 2 option(s)

All classes must explicitly define a constructor.

A constructor can be declared private.

A constructor can declare a return value.

A constructor must initialize all the member variables of a class.

A constructor can access the non-static members of a class.

Q17. Which of the following option(s) correctly declare(s) a variable that can directly reference an array of 10 ints?

Select 2 option(s)

int[ ] iA

int[10] iA

int iA[ ]

Object[ ] iA

Object[10] iA

Q18. Is it possible to create arrays of length zero?

Select 1 option(s)

Yes, you can create arrays of any type with length zero.

Yes, but only for primitive datatypes.

Yes, but only for arrays of object references.

Yes, and it is same as a null array.

No, arrays of length zero do not exist in Java.

None

Q19. Which of the following will not give any error at compile time and run time?

Select 4 option(s)

if (8 == 81) {}

if (x = 3) {} // assume that x is an int

if (true) {}

if (bool = false) {} //assume that bool is declared as a boolean

if (x == 10 ? true:false) { } // assume that x is an int

Q20. Which of the following statements are true?

Select 3 option(s)

The condition expression in an if statement can be a method call.

If a and b are of type boolean, the expression (a = b) can be used as the condition expression of an if statement.

An if statement can have either an 'if' clause or an 'else' clause.

The statement : if (false) ; else ; is illegal.

Only expressions which evaluate to a boolean value can be used as the condition in an if statement.

Q21. Which clause(s) are used by a module definition that uses a service?

Select 2 option(s)

exports

provides

uses

implements

requires

Q22. Which of the following statements are true?

Select 2 option(s)

method length() of String class is a final method.

You can make mutable subclasses of the String class.

StringBuilder extends String.

StringBuilder is a final class.

String class is not final.

Q23. Identify examples of autoboxing.

Select 3 option(s)

Long l = Long.valueOf(200);

Integer i = 10;

Integer getValue(){ return 2; }

Long getValue(){ return 2; }

System.out.println(2+"");

String s = (String) ( 1 + 2);

Q24. Which of the following operators can be used in conjunction with a String object?

Select 3 option(s)

Q25. Consider the following class...

class MyString extends String{
MyString(){ super(); }
}

The above code will not compile.

Select 1 option(s)

True

False

None

Q26. Which of these methods can be invoked on a String?

Select 5 option(s)

isBlank()

isEmpty()

lines()

isNull()

strip()

indent(int n)

Q27. Which of the following statements is/are true about java.util.function.IntFunction?

Select 1 option(s)

It represents a function that returns an int primitive.

It avoids additional cost associated with autoboxing/unboxing.

It extends java.util.function.Function

It cannot be parameterized as it is meant to deal only with int primitives.

None

Q28. Which of the following are valid command line options and their one character shortcuts related to the Java module system?

Select 2 option(s)

--module -p

--module-path -p

--module-source-path -s

---module-source-path -m

--list-modules -l

--show-module-resolution -s

--module -m

Q29. Identify correct statements about the Java module system.

Select 2 option(s)

If a request is made from an automatic module to load a type whose package is not defined in any known module then the module system will attempt to load it from the classpath.

The unnamed module can only access types present in the unnamed module.

Code from a named module can access classes that are on the classpath.

If a package is defined in both a named module and the unnamed module then the package in the unnamed module is ignored.

An automatic module cannot access classes from the unnamed module.

Q30. You have a method that currently does not handle any exception thrown from the code contained in its method body. You are now changing this method to call another method that throws IOException.

What changes, independent of each other, can you make to your method so that it will compile?

Select 2 option(s)

Set the exception to null and don't rethrow it.

Declare IOException in the throws clause of your method.

Wrap the call to another method within a try-catch block that catches RuntimeException.

Wrap the call to another method within a try-catch block that catches Exception.

Q31. Which of the following elements is/are a must in a stream pipeline?

Select 2 option(s)

a source

an intermediate operation

a terminal operation

a reduction operation

a method reference

a lambda expression

Q32. Which of the following classes should you use to represent just a date without any time or zone information?

Select 1 option(s)

java.util.Date

java.sql.Date

java.time.Date

java.time.LocalDate

None

Q33. Which of these statements concerning interfaces are true?

Select 3 option(s)

An interface may extend an interface.

An interface may extend a class and may implement an interface.

A class can implement an interface and extend a class.

A class can extend an interface and can implement a class.

An interface can only be implemented and cannot be extended.

All methods of an interface are public and abstract.

An interface may extend a sealed interface.

Q34. Which of the following are true about the "default" constructor?

Select 1 option(s)

It is provided by the compiler only if the class and any of its super classes does not define any constructor.

It takes no arguments.

A default constructor is used to return a default value.

To define a default constructor, you must use the default keyword.

It is always public.

None

Q35. You have created several threads in your application. To ensure that important tasks are performed quickly, you have increased the priority of some threads and lowered the priority of others. At run time, however, you observe that the lower priority threads rarely get a chance to run.

What is this problem called?

Select 1 option(s)

Deadlock

Livelock

Thrashing

Starvation

None

Q36. Which of the following statements regarding inner classes are true ?

Select 3 option(s)

A non static inner class may have static members.

Anonymous inner classes cannot have any 'extends' or 'implements' clause.

Anonymous inner classes can only be created for interfaces.

Anonymous inner classes can never have initialization parameters.

Anonymous inner classes cannot be static.

Q37. Identify correct statements regarding System.in.

Select 2 option(s)

System.in refers to the standard input stream of a Java program. It is opened when the program is started.

System.in refers to the standard input stream of a Java program. It is opened when the program tries to read from the stream for the first time.

The System.in variable cannot be reassigned to any other stream directly.

It is opened when the program is started and cannot be closed explicitly. It is closed when the program ends.

The declared type of System.in is java.io.ObjectInputStream.

It is meant to read a stream of characters.

Q38. Which of the following options can be a part of a correct inner class declaration or a combined declaration and instance initialization?

(Assume that SimpleInterface and ComplexInterface are interfaces.)

Select 2 option(s)

private class C { }

new SimpleInterface() {
//valid code
}

new ComplexInterface(x) {
//valid code
}

private final abstract class C { }

new ComplexClass() implements SimpleInterface { }

Q39. Java Module system achieves which of the following objectives for a Java project?

Select 3 option(s)

It encapsulates the project.

It encapsulates the packages.

It provides a central repository for keeping classes.

It enables a project to manage multiple versions of dependencies.

It provides a reliable mechanism to let components of an application specify their dependencies on other components of the same application.

It provides a way to specify services and declare dependence on such services.

Q40. Which of the following interface is suitable for a class that stores associations of keys to values?

Select 1 option(s)

Collection

SortedSet

Map

Set

None of the above.

None

Q41. Your application requires to store name value pairs such that the order of entries returned while iterating through the structure is deterministic. In other words, if you iterate over the same structure twice, the order of elements returned in both the iterations will be the same. Which of the following classes would you use?

Select 2 option(s)

HashMap

LinkedHashSet

Hashtable

LinkedHashMap

TreeMap

Q42. What will the following code print?

public class TestClass{

static char ch;
static float f;
static boolean bool;

public static void main(String[] args){
System.out.print(f);
System.out.print(" ");
System.out.print(ch);
System.out.print(" ");
System.out.print(bool);
}
}

Select 1 option(s)

0.0 false

0.0f false

0.0 0 false

0.0 true

0.0f true

0.0f 0 true

None

Q43. Identify examples of autoboxing.

Select 3 option(s)

Float f = 2.0;

Float f = 2.0f;

Byte b = 2;

Character c = 2;

String s = "x";

Q44. Identify correct statements about a two dimensional array.

Select 1 option(s)

It is like a rectangular matrix where number of rows and number of columns may be different but each row or each column have the same number of elements.

It is like a square matrix where number of rows and number of columns are same and each row or each column have the same number of elements.

The number of rows and columns must be specified at the time it is declared.

It is basically an array of arrays.

None

Q45. Which of these statements are true?

Select 2 option(s)

A super( < appropriate list of arguments > ) or this( < appropriate list of arguments > ) call must always be provided explicitly as the first statement in the body of the constructor.

If a subclass does not have any declared constructors, the implicit default constructor of the subclass will have a call to super( ).

If neither super( ) or this( ) is declared as the first statement of the body of a constructor, then this( ) will implicitly be inserted as the first statement.

super(< appropriate list of arguments >) can only be called in the first line of the constructor but this(< appropriate list of arguments >) can be called from anywhere.

You can either call super(< appropriate list of arguments >) or this(< appropriate list of arguments >) but not both from a constructor.

Q46. Identify the concrete classes that can be used to store key - value pairs?

Select 2 option(s)

java.util.HashMap

java.util.Set

java.util.SortedSet

java.util.Map

java.util.SortedMap

java.util.TreeMap

Q47. Identify true statement(s) about migrating an application to modules.

Select 1 option(s)

In bottom-up migration all classes and jars get moved to the module-path.

In top-down migration all packages/jars are moved to the module-path.

In top-down migration, the dependencies are migrated first.

Unnamed modules become automatic modules in top-down migration.

In both the approaches for migration, classpath can be used.

None

Q48. Which of the following statements are correct?

Select 2 option(s)

A List stores elements in a sorted order.

A Set keeps the elements sorted and a List keeps the elements in the order they were added.

A SortedSet keeps the elements in the order they were added.

An OrderedSet keeps the elements sorted.

An OrderedList keeps the elements ordered.

A NavigableSet keeps the elements sorted.

Calling addFirst/addLast on TreeSet throws UnsupportedOperationException.

Q49. Which of these statements concerning the use of collection interfaces of the Java standard class library are true?

Select 1 option(s)

None of the standard collection classes are thread safe.

HashSet implements SortedSet.

Collection classes implementing List cannot have duplicate elements.

ArrayList can only accommodate a fixed number of elements.

Some operations may throw an UnsupportedOperationException.

None

Q50. Which of the following are benefits of an array over an ArrayList ?

Select 2 option(s)

It consumes less memory.

Accessing an element in an array is faster than in ArrayList.

You do not have to worry about thread safety.

It implements Collection interface and can thus be passed where ever a Collection is required.

Time's up