Java Standard Test 15 – Java SE 21 Certification

Java Practice Test 15 continues the Free Java SE 21 Developer Professional certification exam 1Z0-830 practice tests for people who need a hiring plan, not another bookmark. Telecom and connectivity companies run huge customer and network systems, and many of those systems are Java. A certification will not teach you a company’s internal tools, but it can show you are serious about the language those teams already use.

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Welcome to your Standard Test 15 – 2025

Name

Phone

Q1. Given:

ReadWriteLock rl = new ReentrantReadWriteLock();
Lock rlock = rl.readLock();
Lock wlock = rl.writeLock();

Identify correct statements regarding code that appears after the above code.
(Consider each option individually.)

Select 3 option(s):

rlock.lock();
System.out.println("read lock acquired");
wlock.lock();
System.out.println("write lock acquired");

This code will print both the statements.

wlock.lock();
System.out.println("write lock acquired");
rlock.lock();
System.out.println("read lock acquired");

This code will print both the statements.

rlock.lock();
System.out.println("read lock acquired");
rlock.lock();
System.out.println("read lock acquired again");

This code will print both the statements.

rlock.lock();
rlock.lock();
rlock.unlock();
wlock.lock();
System.out.println("write lock acquired");

This code will print the statement.

rlock.lock();
try{
wlock.tryLock();
System.out.println("write lock acquired");
}catch(Exception e) {
e.printStackTrace();
}

This code will print an exception stack trace.

rlock.lock();
try{
wlock.tryLock();
wlock.unlock();
System.out.println("write lock acquired ");
}catch(Exception e) {
e.printStackTrace();
}

This code will print an exception stack trace.

Q2. What is the result of compiling and running the following program?

public class Learner {
public static void main(String[] args) {
var dataArr = new String[4];
dataArr[1] = "Bill";
dataArr[2] = "Steve";
dataArr[3] = "Larry";
try{
for(String data : dataArr){
System.out.print(data+" ");
}
}catch(Exception e){
System.out.println(e.getClass());
}
}
}

Select 1 option(s):

Bill Steve Larry null

Bill Steve Larry java.lang.NullPointerException

java.lang.Exception Bill Steve Larry

Bill Steve Larry java.lang.Exception

null Bill Steve Larry

None

Q3. Given:

Path p1 = Paths.get("c:\\temp\\test1.txt");
Path p2 = Paths.get("c:\\temp\\test2.txt");

Which of the following code fragments moves the file test1.txt to test2.txt, even if test2.txt exists?

Select 2 option(s):

Files.move(p1, p2);

Files.move(p1, p2, StandardCopyOption.REPLACE_EXISTING);

try(Files.move(p1, p2)){
}

try(Files.copy(p1, p2, StandardCopyOption.REPLACE_EXISTING)){
Files.delete(p1);
}

Files.copy(p1, p2, StandardCopyOption.REPLACE_EXISTING);
Files.delete(p1);

Q4. What will be the result of compilation and execution of the following code ?

IntStream is1 = IntStream.range(0, 5); //1
OptionalDouble x = is1.average(); //2
System.out.println(x); //3

Select 1 option(s):

It will print 2.5

It will print 2.0

It will print OptionalDouble[2.0]

It will print OptionalDouble[3.0]

It will print 2.0 if line at //2 is replaced with double x = is1.average();

It will print 2.5 if line at //2 is replaced with double x = is1.average();

None

Q5. What will the following code print when run?

class A {
}

class AA extends A {
}

public class TestClass {
public static void main(String[] args) throws Exception {
A a = new A();
AA aa = new AA();
a = aa;
System.out.println("a = "+a.getClass());
System.out.println("aa = "+aa.getClass());
}
}

Select 1 option(s):

It will not compile.

It will throw ClassCastException at runtime.

a = class AA
aa = class AA

a = class A
aa = class AA

None

Q6. Given:

public static void createFile(String name) throws Exception{
try (
OutputStream os = new FileOutputStream(name); ) {

//INSERT CODE HERE

//flush and close the streams that are open
}

}

Which of the following combinations of the lines of code and their outcome when inserted above, are correct?

Select 2 option(s):

DataOutputStream dos = new DataOutputStream(os);
dos.write(1);
A file of size 4 bytes will be created.

os.write(1);
A file of size 1 byte will be created.

BufferedOutputStream bos = new BufferedOutputStream(os);
DataOutputStream dos = new DataOutputStream(bos);
dos.write(1);
A file of size 1 byte will be created.

os.writeInt(1);
A file of size 4 bytes will be created.

Q7. Consider the following program :

class Test{
public static void main(String[] args){
short s = 10; // 1
char c = s; // 2
s = c; // 3
}
}

Identify the correct statements.

Select 2 option(s):

Line 3 is not valid.

Line 2 is not valid.

It will compile because both short and char can hold 10.

None of the lines 1, 2 and 3 is valid.

Q8. What will be the result of attempting to compile and run the following program?

public class TestClass{
public static void main(String args[ ] ){
String s = "hello";
StringBuilder sb = new StringBuilder( "hello" );
sb.reverse();
s.reverse();
if( s == sb.toString() ) System.out.println( "Equal" );
else System.out.println( "Not Equal" );
}
}

Select 1 option(s):

Compilation error.

It will print Equal

It will print Not Equal

Runtime error.

None of the above.

None

Q9. Consider the following program:

import java.util.*;
public class TestClass
{
static String[] sa = { "a", "aa", "aaa", "aaaa" };
static
{
Arrays.sort(sa);
}
public static void main(String[] args)
{
String search = "";
if(args.length != 0) search = args[0];
System.out.println(Arrays.binarySearch(sa, search));
}
}

What are all possible values this program can print when run?

Select 1 option(s):

Any number from -5 to 5 except -1.

Any number from -5 to 3.

Any number from -5 to 3 except -1.

One of a, aa, aaa, or aaaa.

One of a, aa, aaa, aaaa, or null.

Any number from -5 to 5.

None

Q10. Given the following code:

class M { }
class N{
private M m = new M();
public void makeItNull(M pM){
pM = null;
}
public void makeThisNull(){
makeItNull(m);
}
public static void main(String[] args){
N n = new N();
n.makeThisNull();
}
}

Which of the following statements are correct?

Select 1 option(s):

There are no instances of M to be garbage collected till the program ends.

A call to n.makeThisNull() marks the private instance of M for garbage collection.

Setting pM = null; in makeItNull(), marks the private instance of M for garbage collection.

private members of a class become eligible for garbage collection only when the instance of the class itself becomes eligible for garbage collection.

None

Q11. Given:

public class FunWithArgs {
public static void main(String[][] args) {
System.out.println(args[0][1]);
}
public static void main(String[] args) {
var fwa = new FunWithArgs();
String[][] newargs = {args};
fwa.main(newargs);
}
}

The above program is compiled with the command line:
javac FunWithArgs.java
and then run with:
java FunWithArgs a b c

What will be the output?

Select 1 option(s):

It will not compile.

It will throw ArrayIndexOutOfBoundsException at run time.

It will print b

It will print null

None

Q12. Identify the correct statements about the following code:

import java.util.*;
class Person {
private String name;
public Person(String name) { this.name = name; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }

public String toString() { return name; }
}

class Helper {

public void helpPeople(Queue people, Queue helped) {
do {
Person p = (Person) people.poll();
System.out.println("Helped : " + p + " ");
helped.offer(p.getName());
} while (!people.isEmpty());
}

public static void main(String[] args) {
Queue q = new LinkedList();
q.offer(new Person("Pope"));
q.offer(new Person("John"));
Queue helpedQ = new LinkedList();
Helper h = new Helper();
h.helpPeople(q, helpedQ);
}
}

Select 2 option(s):

It will print :
Helped : Pope
Helped : John

It will compile with a warning.

It will throw an exception at runtime.

It will compile without warning but will throw an exception at runtime.

It will print :
Helped : John
Helped : Pope

It will print : Helped : John

It will print : Helped : Pope

Q13. Consider the following code:

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
public class MyCache {
private CopyOnWriteArrayList cal = new CopyOnWriteArrayList();

public void addData(List list){
cal.addAll(list);
}

public int getCacheSize(){
return cal.size();
}
}

Given that one thread calls the addData method on an instance of the above class with a List containing 10 Strings and another thread calls the getCacheSize method on the same instance at the same time, which of the following options are correct?

(Assume that no other calls have been made on the MyCache instance.)

Select 1 option(s):

The getCacheSize call may return any value between 0 and 10.

The getCacheSize call may return either 0 or 10.

The call to getCacheSize will be blocked until the call to addData finishes.

One of the threads may get a ConcurrentModificationException.

None

Q14. Given:

sealed class Automobile permits Car, Bus{
}
final class Car extends Automobile{
}
final class Bus extends Automobile{
}

What can be inserted in the following method code?

public static Automobile getSomething(){
final int x = 1;
return switch(x){
case 0 -> new Car();

INSERT CODE HERE

};
}

Select 2 option(s):

default: return new Bus();

default -> new Bus();

case 1 -> new Bus();
default -> new Automobile();

case 1 -> new Bus();

default: { return new Bus(); }

Q15. What can be inserted in the following code so that it will print exactly 2345 when compiled and run?

public class FlowTest {

static int[] data = {1, 2, 3, 4, 5};

public static void main(String[] args) {
for (var i : data) {
if (i < 2) {
//insert code1 here
}
System.out.print(i);
if (i == 3) {
//insert code2 here
}
}
}
}

Select 2 option(s):

break;
and
//nothing is required

continue;
and
//nothing is required

continue;
and
continue;

break;
and
continue;

break;
and
break;

Q16. What will the following code print when compiled and run?

BiPredicate bip = (s, i)-> s.length()>i; //1
BiFunction bif = (s, i)-> { //2
if(bip.test(s, i)){ //3
return s.substring(0, i);
}
else return s;
};
String str = bif.apply("hello world", 5); //4
System.out.println(str);

Select 1 option(s):

hello

compilation failure at //1

compilation failure at //2

compilation failure at //3

compilation failure at //4

None

Q17. Given the following classes and declarations, which of these statements about //1 and //2 are true?

class A{
private int i = 10;
public void f(){}
public void g(){}
}

class B extends A{
public int i = 20;
public void g(){}
}

public class C{
A a = new A();//1
A b = new B();//2
}

Select 1 option(s):

System.out.println(b.i); will print 10.

The statement b.f( ); will cause compile time error.

System.out.println(b.i); will print 20

All of the above are correct.

None of the above statements is correct.

None

Q18. What will be the output when the following class is compiled and run?

class ScopeTest{
static int x = 5;
public static void main(String[] args){
int x = ( x=3 ) * 4; // 1
System.out.println(x);
}
}

Select 1 option(s):

It will not compile because line //1 cannot be parsed correctly.

It will not compile because x is used before initialization.

It will not compile because there is an ambiguous reference to x.

It will print 12.

It will print 3 .

None

Q19. Given:

public class TestClass {
static int count = 0;

public static void main(String[] args) throws Exception{
ExecutorService es = Executors.newFixedThreadPool(5);
for(int i=0; i<5; i++){
es.submit( () ->
{
for(int j=0; j<5000; j++){
TestClass.count++;
}
}
);
}
es.awaitTermination(10, TimeUnit.SECONDS);
es.shutdownNow();
System.out.println(count);
}

}

Identify correct statement(s) about the above code.

Select 2 option(s):

The count variable is thread safe.

The count variable should be declared volatile to make it thread safe.

The main method should be declared synchronized to make it thread safe.

The code should increment the count variable inside a synchronized block and print it inside a synchronized block that synchronizes on a single common object to make it thread safe.

The count variable should be declared synchronized to make it thread safe.

The code should use AtomicInteger instead of int for count variable to make it thread safe.

Q20. What will the following code print?

-1 -1

1 1

-1 -3

1 3

None

Q21. Given:

String sentence1 = "Carpe diem. Seize the day, boys. Make your lives extraordinary.";
String sentence2 = "Frankly, my dear, I don't give a damn!";
String sentence3 = "Do I look like I give a damn?";
List sentences = Arrays.asList(sentence1, sentence2, sentence3);

Which of the following options will create a stream containing all the words in the three sentences without repetition?

Select 1 option(s):

Stream< String > strm = sentences.stream()
.flatMap(str->Stream.of(str.split("[ ,.!?\r\n]")))
.filter(s->s.length()>0)
.distinct();

Stream< String > strm = sentences.stream()
.map(str->Stream.of(str.split("[ ,.!?\r\n]")))
.filter(s->s.length()>0)
.distinct();

Stream< String > strm = sentences.stream()
.forEach(str->Stream.of(str.split("[ ,.!?\r\n]")))
.filter(s->s.length()>0)
.distinct();

Stream< String > strm = sentences.stream()
.flatMap(str->Stream.of(str.split("[ ,.!?\r\n]")))
.filter(s->s.length()>0)
.merge();

Stream< String > strm = sentences.stream()
.flatMap(str->str.split("[ ,.!?\r\n]"))
.filter(s->s.length()>0)
.distinct();

None

Q22. Given:

List l1 = Arrays.asList("a", "b");
List l2 = Arrays.asList("1", "2");

Which of the following lines of code will print the following output?
a
b
1
2

Select 1 option(s):

Stream.of(l1, l2).forEach((x)->System.out.println(x));

Stream.of(l1, l2).flatMap((x)->Stream.of(x)).forEach((x)->System.out.println(x));

Stream.of(l1, l2).flatMap((x)->x.stream()).forEach((x)->System.out.println(x));

Stream.of(l1, l2).flatMap((x)->x.iterator()).forEach((x)->System.out.println(x));

None

Q23. Consider the following code in which searchBook() method has an inner class.

public class BookStore
{
private static final int taxId = 300000;
private String name;
public String searchBook( final String criteria )
{
int count = 0;
int sum = 0;
sum++;
class Enumerator
{
String iterate( int k)
{
//line 1
return "";
}
// lots of code.....
}
// lots of code.....
return "";
}
}

Which variables are accessible at line 1?

Select 5 option(s):

taxId

name

criteria

count

sum

Q24. Given that Daylight Savings Time ends on Nov 1 at 2 AM in US/Eastern time zone, what will the following code print -

LocalDateTime ld = LocalDateTime.of(2022, Month.OCTOBER, 31, 10, 0);

ZonedDateTime date = ZonedDateTime.of(ld, ZoneId.of("US/Eastern"));
date = date.plus(Duration.ofDays(1));
System.out.println(date);

date = ZonedDateTime.of(ld, ZoneId.of("US/Eastern"));
date = date.plus(Period.ofDays(1));
System.out.println(date);

Select 1 option(s):

2022-11-01T09:00-05:00[US/Eastern]
2022-11-01T09:00-05:00[US/Eastern]

2022-11-01T09:00-05:00[US/Eastern]
2022-11-01T10:00-05:00[US/Eastern]

2022-11-01T10:00-05:00[US/Eastern]
2022-11-01T09:00-05:00[US/Eastern]

2022-11-01T10:00-05:00[US/Eastern]
2022-11-01T10:00-05:00[US/Eastern]

None

Q25. What is wrong with the following code?

class MyException extends Exception {}
public class TestClass{
public static void main(String[] args){
TestClass tc = new TestClass();
try{
tc.m1();
}
catch (MyException e){
tc.m1();
}
finally{
tc.m2();
}
}
public void m1() throws MyException{
throw new MyException();
}
public void m2() throws RuntimeException{
throw new NullPointerException();
}
}

Select 1 option(s):

It will not compile because you cannot throw an exception in finally block.

It will not compile because you cannot throw an exception in catch block.

It will not compile because NullPointerException cannot be created this way.

It will not compile because of unhandled exception.

It will compile but will throw an exception when run.

None

Q26. Which statement regarding the following code is correct?

class A{
public int i = 10;
private int j = 20;

}

class B extends A{
private int i = 30; //1
public int k = 40;

}

class C extends B{
}

public class TestClass{
public static void main(String args[]){
C c = new C();
System.out.println(c.i); //2
System.out.println(c.j); //3
System.out.println(c.k);
}
}

Select 1 option(s):

The code will print 10 and 40 if //3 is commented out.

The code will print 40 if //2 and //3 are commented out.

The code will not compile because of //1.

The code will compile if the line marked //2 is commented out.

None of these.

None

Q27. Given:

class MyException extends Exception {
private final int code;
public MyException(int code, Throwable actualEx){
super(actualEx);
this.code = code;
}

public MyException(int code, String message, Throwable actualEx){
super(message, actualEx);//1
this.code = code;
}

public String getMessage(){
return String.format("Exception - Code=%d, Msg=%s, OrigMsg=%s", code,
super.getMessage(), this.getCause().getMessage()); //2
}
}

public class TestClass {
public static void main(String[] args) {
try{
throw new MyException(new IOException("NOT FOUND")); //3
}catch(Exception e){
System.out.println(e.getMessage());
}
}
}

What is the result?

Select 1 option(s):

Compilation failure at //3

It will print:
Exception - Code=0, Msg=null, OrigMsg=NOT FOUND

It will print:
Exception - Code=0, Msg=NOT FOUND, OrigMsg=null

It will print:
Exception - Code=0, Msg=, OrigMsg=null

None

Q28. Given the following two files in /user/home directory:

In file messages.properties:
message=hi {0}, thanks {1}

In file messages_fr_FR.properties:
message=salut {0}, merci {1}

and the following class in /user/home directory:

public class TestClass
{
public static void main(String[] args) {

//INSERT CODE HERE
System.out.println(message);
}
}

Which of the following options when inserted in TestClass will print salut Amy, merci Adams?

Select 2 option(s):

ResourceBundle msg = ResourceBundle.getBundle("/user/home/messages",
new Locale("fr", "FR"));
Object[] names = { "Amy", "Adams" };
String message = MessageFormat.format(msg.getString("message") , names);

ResourceBundle msg = ResourceBundle.getBundle("messages.messages", Locale.FRANCE);
Object[] names = { "Amy", "Adams" };
String message = MessageFormat.format(msg.getString("message") , names);

ResourceBundle msg = ResourceBundle.getBundle("messages", new Locale("fr", "FR"));
Object[] names = { "Amy", "Adams" };
String message = MessageFormat.format(msg.getString("message") , names);

Locale.setDefault(Locale.FRANCE);
ResourceBundle msg = ResourceBundle.getBundle("messages");
String message = MessageFormat.format(msg.getString("message") , "Amy", "Adams");

Q29. Given:

public static void reader(String fileName1) throws Exception{
try (var fr = new FileReader(fileName1);) {
int charRead = 0;
while ((charRead = fr.read()) != -1) {
System.out.println("Read char " + charRead);
}
}
}

What can be done to the above code to make it read Strings instead of chars?

Select 1 option(s):

Chain fr to a StringReader and use its readString method.

Use fr.readString instead of fr.read.

Chain fr to a BufferedReader use its readLine method

Chain fr to a DataReader and use its readLine method.

None

Q30. Given:

List letters = Arrays.asList("j", "a", "v","a");
Which of the following code snippets will print JAVA?

Select 3 option(s):

letters.forEach(letter->letter.toUpperCase());
letters.forEach(System.out::print);

UnaryOperator < String > uo = str->str.toUpperCase();
letters.forEach(uo);
letters.forEach(System.out::print);

UnaryOperator< String > uo = str->str.toUpperCase();
letters.replaceAll(uo);
letters.forEach(System.out::print);

letters.forEach(letter->System.out.print(letter.toUpperCase()));

System.out.print(letters.stream().collect(Collectors.joining()).toUpperCase());

System.out.print(
letters.stream().collect(Collectors.joining(letter->letter.toUpperCase()));
);

Q31. Which of these array declarations and instantiations are legal?

Select 4 option(s):

int[ ] a[ ] = new int [5][4] ;

int a[ ][ ] = new int [5][4] ;

int a[ ][ ] = new int [ ][4] ;

int[ ] a[ ] = new int[4][ ] ;

int[ ][ ] a = new int[5][4] ;

var[ ] a[ ] = new int [5][4] ;

var[ ][ ] a = new int [5][4] ;

Q32. Given the following class, which of the given blocks can be inserted at line 1 without errors?

public class InitClass{
private static int loop = 15 ;
static final int INTERVAL = 10 ;
boolean flag ;
//line 1
}

Select 4 option(s):

static {System.out.println("Static"); }

static { loop = 1; }

static { loop += INTERVAL; }

static { INTERVAL = 10; }

{ flag = true; loop = 0; }

var flag2 = flag ;

Q33. Assume the following declarations:

class A{ }
class B extends A{ }
class C extends B{ }

class X{
B getB(){ return new B(); }
}

class Y extends X{
//method declaration here
}

Which of the following methods can be inserted in class Y?

Select 2 option(s):

public C getB(){ return new B(); }

protected B getB(){ return new C(); }

C getB(){ return new C(); }

A getB(){ return new A(); }

Q34. What will the following code print?

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

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

Q35. Consider the following classes :

interface I{
}

class A implements I{
}

class B extends A {
}

class C extends B{
}
And the following declarations:
A a = new A();
B b = new B();

Identify options that will compile and run without error.

Select 1 option(s):

a = (B)(I)b;

b = (B)(I) a;

a = (I) b;

I i = (C) a;

None

Q36. Given:

class TestClass{
public static void main(String[] args) throws IOException {

final InputStream fis = new FileInputStream("c:\\temp\\test.txt");
long l = 0;
try(fis){
l = fis.read();//1
}finally{
l = fis.read();//2
}
l = fis.read();//3
System.out.println(l);//4
}
}

Assuming that c:\\temp\\test.txt is readable, what will be the output?

Select 1 option(s):

Compilation failure.

Exception at //1.

Exception at //2.

Exception at //3.

Value of the first byte in the file will be printed.

Value of the second byte in the file will be printed.

None

Q37. Given:

Map hm = new ConcurrentHashMap();
hm.put(null, "asdf"); //1
hm.put("aaa", null); //2

hm = new HashMap();
hm.put(null, "asdf"); //3
hm.put("aaa", null); //4

List list = new ArrayList();
list.add(null); //5
list.add(null); //6

list = new CopyOnWriteArrayList();
list.add(null); //7

Which of the above lines will throw NullPointerException?
(Assume that each of the put and add calls are executed as if they are wrapped inside a try/catch block i.e. an exception thrown at //1 will not prevent the execution of //2.)

Select 2 option(s):

//1

//2

//3

//4

//5

//6

//7

Q38. Given:

class M {
static Object obj = null;
public M(String val){ obj = val; }
}

class N{

private M m = new M("hello");

public static void main(String[] args){
N n = new N();
n = null;
System.gc();
System.out.println(M.obj);
}
}

Assuming that System.gc() does its job, what will be printed?

Select 1 option(s):

null

It will throw a NullPointerException at run time.

hello

It will thrown an IllegalAccessException at run time.

It will not compile.

None

Q39. Given the following class:

public class Food{ // LINE 1
String name;
int caloriesPerServing;
public Food(String name, int calories){
this.name = name; this.caloriesPerServing = calories;
}
//accessors not shown

//LINE 2
}

This class is used in an application as follows -

ArrayList al = new ArrayList();
//code that adds Food objects to al not shown
Collections.sort(al);

What changes must be done to Food class so that the call to Collections.sort(al) will work as expected?

Select 2 option(s):

Replace line 1 with :
public class Food implements Comparable< Food >{

Replace line 1 with :
public class Food implements Comparator< Food >{

Replace line 1 with :
public class Food extends Comparator< Food >{

Replace line 1 with :
public class Food extends Comparable< Food >{

Add the following a line 2 :
public int compareTo(Food f){
return this.name.compareTo(f.name);
}

Add the following a line 2 :
public boolean compare(Food f){
return this.name.compare(f.name);
}

Add the following a line 2 :
public int compare(Food f){
return this.name.compare(f.name);
}

Q40. Given:

List primes = Arrays.asList(2, 3, 5, 7, 11, 13, 17); //1
Stream primeStream = primes.stream(); //2

Predicate test1 = k->k<10; //3
long count1 = primeStream.filter(test1).count();//4

Predicate test2 = k->k>10; //5
long count2 = primeStream.filter(test2).count(); //6

System.out.println(count1+" "+count2); //7

Identify correct statements.

Select 1 option(s):

It will print 4 3 if line at //6 is replaced with:
long count2 = primeStream.reset().filter(test2).count(); //6

It will print 4 3 if types of count1 and count2 are changed to int.

It will print 4 3 if line //4 and //6 are replaced with:
long count1 = IntStream.of(primes).filter(test1).count();//4
and
long count2 = IntStream.of(primes).filter(test2).count();//6

It will print 34 or 43 if lines 4 to 7 are replaced with:
primeStream.collect(Collectors.partitioningBy(test1, Collectors.counting()))
.values().forEach(System.out::print);

None

Q41. Consider the following classes :

class A{
public static void sM1() { System.out.println("In base static"); }
}

class B extends A{

Line 1 --> // public static void sM1() { System.out.println("In sub static"); }

Line 2 --> // public void sM1() { System.out.println("In sub non-static"); }

}

Which of the following statements are true?

Select 2 option(s):

class B will not compile if line 1 is uncommented.

class B will not compile if line 2 is uncommented.

class B will not compile if line 1 and 2 are both uncommented.

Only the second option is correct.

Only the third option is correct.

Q42. Given:

class MyProcessor{
int value;
public MyProcessor(){ value = 10; }
public MyProcessor(int value){
this.value = value;
}
public void process(){
System.out.println("Processing "+value);
}
}

Which of the following code snippets will print Processing 10?

Select 2 option(s):

Supplier< MyProcessor > supp = MyProcessor::new;
MyProcessor mp = supp.get();
mp.process();

Supplier< MyProcessor > supp = MyProcessor::new(10);
MyProcessor mp = supp.get();
mp.process();

Supplier< MyProcessor > supp = MyProcessor(10)::new;
MyProcessor mp = supp.get();
mp.process();

Function< Integer, MyProcessor > f = MyProcessor::new;
MyProcessor mp = f.apply(10);
mp.process();

MyProcessor mp = MyProcessor::new(10);
mp.process();

Q43. Which of these for statements are valid when present in a method?

1. for (var i=5; i=0; i--) { }

2. var j=5;
for(int i=0, j+=5; i<j ; i++) { j--; }

3. int i, j;
for (j=10; i<j; j--) { i += 2; }

4. var i=10;
for ( ; i>0 ; i--) { }

5. for (int i=0, j=10; i<j; i++, --j) {;}

6. for (var i=0, j=10; i<j; i++, --j) {;}

Select 1 option(s):

1, 2

3, 4

1, 5

4, 5

4, 5, 6

None

Q44. Consider the following interface definition:

public interface ConstTest{

public int A = 1; //1

int B = 1; //2

static int C = 1; //3

final int D = 1; //4

public static int E = 1; //5

public final int F = 1; //6

static final int G = 1; //7

public static final int H = 1; //8

}

Which line(s) will cause a compilation error?

Select 1 option(s):

None of them will cause any error.

None

Q45. Consider the following code:

class OuterWorld
{
public InnerPeace i = new InnerPeace("none"); //1
class InnerPeace
{
private String reason = "none";
InnerPeace(String reason){ this.reason = reason; }
}
public static void main(String[] args){
var ip = new InnerPeace("yoga"); //2
var out = new OuterWorld();
System.out.println(out.i.reason); //3
}
}

Identify correct statements about the above code.

Select 2 option(s):

Compilation error at //1

Compilation error at //2

Compilation error at //3

code at //2 can be compiled if InnerPeace definition changed to:
private static class InnerPeace ...

code at //2 can be compiled if InnerPeace definition is moved to a separate InnerPeace.java file without impacting other parts of the code.

Q46. Consider these two interfaces:

interface I1
{
void m1() throws java.io.IOException;
}
interface I2
{
void m1() throws java.io.FileNotFoundException;
}

Which of the following are valid method declarations for a class that says it implements I1 and I2 ?

Select 1 option(s):

Both, public void m1() throws FileNotFoundException; and public void m1() throws IOException;

public void m1() throws FileNotFoundException

The class cannot implement both the interfaces as they have conflicting methods.

public void m1() throws Exception;

None of the above.

None

Q47. Identify the correct statements about the following code:

import java.util.*;
class Person {
private static int count = 0;
private String id = "0"; private String interest;
public Person(String interest){ this.interest = interest; this.id = "" + ++count; }
public String getInterest(){ return interest; }
public void setInterest(String interest){ this.interest = interest; }
public String toString(){ return id; }
}

public class StudyGroup
{
String name = "MATH";
TreeSet set = new TreeSet();
public void add(Person p) {
if(name.equals(p.getInterest())) set.add(p);
}

public static void main(String[] args) {
StudyGroup mathGroup = new StudyGroup();
mathGroup.add(new Person("MATH"));
System.out.println("A");
mathGroup.add(new Person("MATH"));
System.out.println("B");
System.out.println(mathGroup.set);
}
}

Select 1 option(s):

It will print : A, B, and then the contents of mathGroup.set.

It will compile with a warning.

It will NOT throw an exception at runtime.

It will compile without warning but will throw an exception at runtime.

It will only print : A

It will print : A and B.

None

Q48. Consider the following code:

//INSERT CODE HERE
a[0][0] = 1;
a[0][1] = 2;

a[1][0] = 3;
a[1][1] = 4;
a[1][2] = 5;
a[1][3] = 6;

What can be inserted independently in the above code so that it will compile and run without any error or exception?

Select 2 option(s):

int[][] a = new int[2][];

int[][] a = new int[2][4];

int[][] a = new int[4][2];

int[][] a = new int[2][];
a[0] = new int[2];
a[1] = new int[4];

int[][] a = new int[4][];
a[0] = new int[2];
a[1] = new int[2];

Q49. Identify correct statements about the following code:

interface Processor {
Iterable process();
}

interface ItemProcessor extends Processor{
Collection process();
}

interface WordProcessor extends Processor{
String process();
}

interface GenericProcessor extends ItemProcessor, WordProcessor{

}

Select 2 option(s):

ItemProcessor fails compilation because it does not override the process method correctly.

WordProcessor fails compilation because it does not override the process method correctly.

GenericProcessor fails compilation because it inherits two process methods with incompatible return types.

GenericProcessor fails compilation because it extends from more than one interface.

WordProcessor will compile without errors if @Override annotation is applied on its process method.

Q50. Given that a class named com.xyz.fx.Main is part of a module named xyz.fx packaged in fx.jar, which of the following commands can be used to execute this class?

(Assume that the jar file is located in the current directory.)

Select 2 option(s):

java -classpath fx.jar --m xyz.fx/com.xyz.fx.Main

java --p fx.jar --m xyz.fx/com.xyz.fx.Main

java -p fx.jar --module xyz.fx/com.xyz.fx.Main

java --module-path fx.jar --module com.xyz.fx.Main

java -classpath fx.jar com.xyz.fx.Main

Time's up