Java SE 21 exam 1Z0-830 practice test 6

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Welcome to your Foundation Test 6 – 2025

Name

Phone

Q1. Assuming that the following code compiles without any error, identify correct statements.

interface Processor {
A process(String str);
}

class ItemProcessor implements Processor{
@Override
public B process(String str){
return new B(str);
}
}

Select 2 option(s):

B must be a sub type of A.

A must be a sub type of B.

There need not be any type - sub type relation between A and B or B and A.

B must be final.

B must not be final.

A cannot be abstract.

B cannot be abstract.

Q2. What is wrong with the following code written in a single file named TestClass.java?

class SomeThrowable extends Throwable { }
class MyThrowable extends SomeThrowable { }
public class TestClass{
public static void main(String args[]) throws SomeThrowable{
try{
m1();
}catch(SomeThrowable e){
throw e;
}finally{
System.out.println("Done");
}
}
public static void m1() throws MyThrowable{
throw new MyThrowable();
}
}

Select 1 option(s):

The main declares that it throws SomeThrowable but throws MyThrowable.

You cannot have more than 2 classes in one file.

The catch block in the main method must declare that it catches MyThrowable rather than SomeThrowable.

There is nothing wrong with the code and Done will be printed.

None

Q3. Which of these statements are true?

Select 2 option(s):

If a RuntimeException is not caught, the method will terminate and normal execution of the thread will resume.

An overriding method must declare that it throws the same exception classes as the method it overrides.

The main method of a program can declare that it throws checked exceptions.

A method declaring that it throws a certain exception class may throw instances of any subclass of that exception class.

finally blocks are executed if and only if an exception gets thrown while inside the corresponding try block.

Q4. Which of the following code fragments are valid method declarations?

Select 1 option(s):

void method1{ }

void method2( ) { }

void method3(void){ }

var method4{ }

method5(void){ }

String method6(var x){ return ""+x; }

sealed void method7(){ }

None

Q5. Which line, if any, will give a compile time error ?

void test(byte x){
switch(x){
case 'a': // 1
case 256: // 2
case 0: // 3
default : // 4
case 80: // 5
}
}

Select 1 option(s):

Line 1 as 'a' is not compatible with byte.

Line 2 as 256 cannot fit into a byte.

No compile time error but a run time error at line 2.

Line 4 as the default label must be the last label in the switch statement.

There is nothing wrong with the code.

None

Q6. How can you declare 'i' so that it is not visible outside the package test.

package test;
public class Test{
XXX int i;
/* irrelevant code */
}

Select 2 option(s):

private

public

protected

No access modifier

friend

Q7. Which of the following correctly defines a method named stringProcessor that can be called by other programmers as follows: stringProcessor(str1) or stringProcessor(str1, str2) or stringProcessor(str1, str2, str3), where str1, str2, and str3 are references to String instances.

Select 1 option(s):

public void stringProcessor(...String){
}

public void stringProcessor(String... strs){
}

public void stringProcessor(String[] strs){
}

public void stringProcessor(String a, String b, String c){
}

public void stringProcessor(var String a){
}

Three separate methods need to be written.

None

Q8. Identify the valid for loop constructs assuming the following declarations:

Object o = null;
Collection c = //valid collection object.
int[][] ia = //valid array

Select 2 option(s):

for(o : c){ }

for(final var o2 : c){ }

for(int i : ia) { }

for(Iterator it : c.iterator()){ }

for(int i : ia[0]){ }

Q9. Which of the following statements are true regarding the try-with-resources statement?

Select 1 option(s):

Resources are closed in the same order of their creation.

Resources may not be closed properly if the code in the try block throws an exception for which there is no catch block.

Resources may not be closed properly if the code in the catch block throws an exception.

catch and finally blocks are executed after the resources opened in the try blocks are closed.

None

Q10. Identify correct constructs.

Select 1 option(s):

try {
for( ;; );
}finally { }

try {
File f = new File("c:\\a.txt");
} catch { f = null; }

int k = 0;
try {
k = callValidMethod();
}
System.out.println(k);
catch { k = -1; }

try {
try {
Socket s = new ServerSocket(3030);
}catch(Exception e) {
s = new ServerSocket(4040);
}
}

try {
s = new ServerSocket(3030);
}
catch(Exception t){ t.printStackTrace(); }
catch(IOException e) {
s = new ServerSocket(4040);
}
catch(Throwable t){ t.printStackTrace(); }

int x = validMethod();
try {
if(x == 5) throw new IOException();
else if(x == 6) throw new Exception();
}finally {
x = 8;
}
catch(Exception e){ x = 9; }

None

Q11. Which of the following statements will compile without any error?

Select 5 option(s):

System.out.println("a"+'b'+63);

System.out.println("a"+63);

System.out.println('b'+ Integer.valueOf(63));

String s = 'b'+63+"a";

String s = 63 + Integer.valueOf(10);

String valueStr = (String) (63 + Integer.valueof(10));

int i = 7;
float j = i%3-2;

Q12. Which of the following are valid declarations inside an interface independent of each other?

Select 2 option(s):

void compute();

public void compute();

public final void compute();

static void compute();

protected void compute();

sealed class MyClass { }

Q13. You have a collection which contains objects of a class X. When the collection is sorted using Collections.sort(collectionOfX);, X's compareTo() method is used. Which of the following statements are correct about this class X?

Select 2 option(s):

Class X implements Comparator interface.

Class X implements Comparable interface.

Class X neither implements Comparable nor Comparator. Object of a separate class that implements Comparator is used for sorting.

The mechanism used in this situation allows the Objects of class X to be sorted in only one way (and the reverse of that way).

Q14. This following code appears in a file named VehicleType.java. Why would it not compile?

//In file VehicleType
package objective1;
public enum VehicleType
{

SUV, SEDAN, VAN, SPORTSCAR;

public VehicleType()
{

}

}

Select 1 option(s):

VehicleType's definition cannot be public.

VehicleType's constructor cannot be public.

package statement is invalid for VehicleType.

VehicleType must be defined as a class instead of enum since it is the only definition in the file.

None

Q15. What will the following lines of code print?

System.out.println(1 + 5 < 3 + 7);
System.out.println( (2 + 2) >= 2 + 3);

Select 1 option(s):

They will not compile.

1false10
false

true
false

false
false

None

Q16. Checked exceptions are meant for...

Select 1 option(s):

exceptional conditions external to an application that a well written application should anticipate and from which it can recover.

exceptional conditions external to the program that a well written program cannot anticipate but should recover from.

exceptional conditions from which recovery is difficult or impossible.

exceptional situations internal to an application that the application can anticipate but cannot recover from.

None

Q17. Encapsulation ensures that ...

Select 1 option(s):

classes are able to inherit functionality from other classes.

classes expose only certain fields and methods to other classes for access.

classes designate certain methods to be abstract and let them be implemented by subclasses.

a method that takes a class X object as a parameter can be passed an object of a subclass of X.

None

Q18. Given:

public class Square {
private double side = 0; // LINE 2

public static void main(String[] args) { // LINE 4
Square sq = new Square(); // LINE 5
side = 10; // LINE 6
}
}

What can be done to make this code compile and run?

Select 1 option(s):

replace // LINE 2 with:
private int side = 0;

replace // LINE 2 with:
public int side = 0;

replace // LINE 5 with:
double sq = new Square();

replace // LINE 6 with:
sq.side = 10;

None

Q19. Given:

int a = 1 + 2 + 3 * 4;
int b = 2 * 3 + 4;

int total = a + b;

What will be the value of total?

Select 1 option(s):

None

Q20. Following is a supposedly robust method to parse an input for a float :

public float parseFloat(String s){
float f = 0.0f;
try{
f = Float.valueOf(s).floatValue();
return f ;
}
catch(NumberFormatException nfe){
System.out.println("Invalid input " + s);
f = Float.NaN ;
return f;
}
finally { System.out.println("finally"); }
return f ;
}

Which of the following statements about the above method is/are true?

Select 1 option(s):

If input is "0.1" then it will return 0.1 and print finally.

If input is "0x.1" then it will return Float.NaN and print Invalid input 0x.1 and finally.

If input is "1" then it will return 1.0 and print finally.

If input is "0x1" then it will return 0.0 and print Invalid input 0x1 and finally.

The code will not compile.

None

Q21. Identify the correct statements about Java Stream API.

Select 1 option(s):

Streams are reusable.

Elements of a stream are mutable.

Streams support aggregate operations.

All Stream operations are lazy.

None

Q22. Consider the following classes...

class Teacher{
void teach(String student){
/* valid code goes below */
}
}
class Prof extends Teacher{
//1
}

Which of the following methods can be inserted at line //1 ?

Select 4 option(s):

public void teach() throws Exception{}

private void teach(int i) throws Exception{}

protected void teach(String s){}

public final void teach(String s){}

public abstract void teach(String s);

Q23. What will the following program print?

public class TestClass{
public static void main(String[] args){
unsigned byte b = 0;
b--;
System.out.println(b);
}
}

Select 1 option(s):

-1

255

-128

It will not compile.

It will throw an exception at run time.

None

Q24. Consider the following code:

Locale.setDefault(new Locale("es", "ES"));
ResourceBundle rb = ResourceBundle.getBundle("appmessages");
String msg = rb.getString("greetings");
System.out.println(msg);

You have created a valid resource bundle file named appmessages_es_ES.properties that contains 'greetings' property. However, when you run the above code, you get an exception saying,
"java.util.MissingResourceException:
Can't find bundle for base name appmessages, locale es_ES".

What could be the reason?

Select 1 option(s):

appmessages_es_ES.properties is not present in PATH.

appmessages_es_ES.properties is not present in CLASSPATH.

appmessages_es_ES.properties is not specified using -D option on command line.

appmessages_es_ES.properties is not present in JAVA_HOME.

None

Q25. Which of the following texts show the right way to specify entries in a resource bundle file?

Select 2 option(s):

greetings=bonjour

< key name="greetings"> bonjour </key >

< key name="greetings" value="bonjour" / >

< key >
< name >greetings< /name >
< value >bonjour"< /value >
< /key >

< key >greetings< /key >
< value >bonjour< /value >

greetings1=bonjour
greetings2=no bonjour

greetings1=bonjour,greetings2=no bonjour

Q26. Given:

class Base{
public Map getMap(T t, Z z)
{
return new HashMap();
}
}

class Derived extends Base{

/* public TreeMap getMap(T t, Z z) {
return new TreeMap();
}; */ //1

/* public Map getMap(Number t, Number z) {
return new TreeMap();
}; */ //2

/* public Map getMap(Number t, Number z) {
return new HashMap();
};*/ //3

}

Identify correct statements about the methods defined in Derived assuming they are uncommented one at a time individually.

Select 1 option(s):

//1 correctly overloads while //2 and //3 correctly override the method in Base.

//1 will not compile while //2 and //3 correctly overload the method in Base.

//1 correctly overloads the method in Base while //2 and //3 will not compile.

//1 correctly overrides while //2 and //3 correctly overloads the method in Base.

//1 and //3 will compile while //2 will not.

//1 and //2 will compile while //3 will not.

None

Q27. Given the following code:

interface Movable{
int offset = 100;
public void move(int dx);
}
interface Growable{
public void grow(int dy);
}

class Animal implements Movable, Growable{
public void move(int dx){ }
public void grow(int dy){ }
}

Select 1 option(s):

Animal class illustrates Java's support for multiple inheritance of type.

Animal class illustrates Java's support for multiple inheritance of state.

Animal class illustrates Java's support for multiple inheritance of type as well as state.

Animal class illustrates Java's support for multiple implementation inheritance.

None

Q28. Which of the following are correct ways to initialize the static variables MAX and CLASS_GUID ?

class Widget{
static int MAX; //1
static final String CLASS_GUID; // 2
Widget(){
//3
}
Widget(int k){
//4
}
}

Select 2 option(s):

Modify lines //1 and //2 as : static int MAX = 111; static final String CLASS_GUID = "XYZ123";

Add the following line just after //2 : static { MAX = 111; CLASS_GUID = "XYZ123"; }

Add the following line just before //1 : { MAX = 111; CLASS_GUID = "XYZ123"; }

Add the following line at //3 as well as //4 : MAX = 111; CLASS_GUID = "XYZ123";

Only option 3 is valid.

Q29. Which of the following correctly identify the differences between a Callable and a Runnable?

Select 3 option(s):

A Callable cannot be passed as an argument while creating a Thread but a Runnable can be.

A Callable needs to implement call() method while a Runnable needs to implement run() method.

A Callable can return a value but a Runnable cannot.

A Callable can be used with ExecutorService but a Runnable cannot be.

A Callable can be used to create a virtual thread but a Runnable cannot be.

Q30. What will the following code snippet print?

int index = 1;
String[] strArr = new String[5];
var myStr = strArr[index];
System.out.println(myStr);

Select 1 option(s):

nothing

null

It will throw ArrayIndexOutOfBounds at runtime.

It will print some junk value.

None of the above.

None

Q31. Consider the following code snippet:

void m1() throws Exception{
try{
// line1
}
catch (IOException e){
throw new SQLException();
}
catch(SQLException e){
throw new InstantiationException();
}
finally{
throw new CloneNotSupportedException();
// CloneNotSupportedException is a checked exception.
}
}

Which of the following statements are true?

Select 2 option(s):

If IOException gets thrown at line1, then the whole method will end up throwing SQLException.

If IOException gets thrown at line1, then the whole method will end up throwing CloneNotSupportedException.

If IOException gets thrown at line1, then the whole method will end up throwing InstantiationException.

If no exception is thrown at line1, then the whole method will end up throwing CloneNotSupportedException.

If SQLException gets thrown at line1, then the whole method will end up throwing InstantiationException.

Q32. You want to invoke the overridden method (the method in the base class) from the overriding method (the method in the derived class) named m().

Which of the following constructs which will let you do that?

Select 1 option(s):

super.m();

super.this();

base.m();

parent.m();

super();

None

Q33. What will the following program print?

public class TestClass{
static String str;
public static void main(String[] args){
System.out.println(str);
}
}

Select 1 option(s):

It will not compile.

It will compile but throw an exception at runtime.

It will print null

It will print nothing.

None of the above.

None

Q34. Which of the given statements are correct for a method that overrides the following method:

public Set getSet(int a) {...}

Assume that Set is an interface and HashSet is a class that implements Set.

Select 3 option(s):

Its return type must be declared as Set.

It may return HashSet.

It can declare any Exception in throws clause

It can declare any RuntimeException in throws clause.

It can be abstract.

Q35. Which of the following method definitions will prevent overriding of that method?

Select 4 option(s):

public final void m1()

public static void m1()

public static final void m1()

public abstract void m1()

private void m1()

public sealed void m1()

Q36. Which of the following are correct about "encapsulation"?

Select 2 option(s):

Encapsulation is same as polymorphism.

It helps make sure that clients have no accidental dependence on the choice of representation

It helps avoiding name clashes as internal variables are not visible outside.

Encapsulation makes sure that messages are sent to the right object at run time.

Encapsulation helps you inherit the properties of another class.

Q37. Given a class named Test, which of these would be valid definitions for a constructor for this class?

Select 1 option(s):

Test(Test b) { }

Test Test( ) { }

private final Test( ) { }

void Test( ) { }

public static void Test(String args[ ] ) { }

None

Q38. Following is a program to capture words from the command line and create two collections. One that keeps only unique words and one that keeps all the words in the order they were entered. What should replace AAA and BBB?

static Collection unique = new AAA();
static Collection ordered = new BBB();
public static void main(String args[]) throws Exception
{
BufferedReader bfr = new BufferedReader( new InputStreamReader( System.in ) );
String s = bfr.readLine();
while(s != null && s.length() >0)
{
unique.add(s);
ordered.add(s);
s = bfr.readLine();
}
System.out.println(unique);
System.out.println(ordered);
}

Select 2 option(s):

Set, List

LinkedList, HashSet

HashSet, LinkedList

HashSet, ArrayList

Vector, TreeSet

Time's up