Java Programming Language Practice Quiz Questions

1.

Given:
10. class Nav{
11. public enum Direction { NORTH, SOUTH, EAST, WEST }
12. }
13. public class Sprite{
14. // insert code here
15. }
Which code, inserted at line 14, allows the Sprite class to compile?

Direction d = NORTH;

Nav.Direction d = NORTH;

Direction d = Direction.NORTH;

Nav.Direction d = Nav.Direction.NORTH;

The correct answer is "Nav.Direction d = Nav.Direction.NORTH;". This is the correct code to insert at line 14 because it specifies the fully qualified name of the Direction enum, which is Nav.Direction.NORTH. This ensures that the compiler can correctly identify the enum and allows the Sprite class to compile without any errors.

Explanation

The correct answer is "Nav.Direction d = Nav.Direction.NORTH;". This is the correct code to insert at line 14 because it specifies the fully qualified name of the Direction enum, which is Nav.Direction.NORTH. This ensures that the compiler can correctly identify the enum and allows the Sprite class to compile without any errors.

2.

Given:
10. interface Foo {}
11. class Alpha implements Foo { }
12. class Beta extends Alpha {}
13. class Delta extends Beta {
14. public static void main( String[] args) {
15. Beta x = new Beta();
16. // insert code here
17. }
18. }
Which code, inserted at line 16, will cause a
java.lang.ClassCastException?

Alpha a = x;

Foo f= (Delta)x;

Foo f= (Alpha)x;

Beta b = (Beta)(Alpha)x;

The code "Foo f= (Delta)x;" will cause a java.lang.ClassCastException. This is because the variable "x" is of type Beta, and the code is trying to cast it to type Delta, which is a subclass of Beta. Since Delta is not a superclass of Beta, the cast will result in a ClassCastException.

Explanation

The code "Foo f= (Delta)x;" will cause a java.lang.ClassCastException. This is because the variable "x" is of type Beta, and the code is trying to cast it to type Delta, which is a subclass of Beta. Since Delta is not a superclass of Beta, the cast will result in a ClassCastException.

3.

Given:
20. public class CreditCard {
21.
22. private String cardlD;
23. private Integer limit;
24. public String ownerName;
25.
26. public void setCardlnformation(String cardlD,
27. String ownerName,
28. Integer limit) {
29. this.cardlD = cardlD;
30. this.ownerName = ownerName;
31. this.limit = limit;
32. }
33. }
Which is true?

The class is fully encapsulated.

The code demonstrates polymorphism.

The ownerName variable breaks encapsulation.

The cardlD and limit variables break polymorphism.

The setCardlnformation method breaks encapsulation.

The ownerName variable breaks encapsulation because it is declared as public, allowing direct access to the variable from outside the class. In encapsulation, variables should be declared as private to restrict direct access and provide controlled access through getter and setter methods.

Explanation

The ownerName variable breaks encapsulation because it is declared as public, allowing direct access to the variable from outside the class. In encapsulation, variables should be declared as private to restrict direct access and provide controlled access through getter and setter methods.

4.

Given:
1. interface TestA { String toString(); }
2. public class Test {
3. public static void main(String[] args) {
4. System.out.println(new TestA() {
5. public String toString() { return "test"; }
6. });
7. }
8. }
What is the result?

Test

Null

An exception is thrown at runtime.

Compilation fails because of an error in line 1.

Compilation fails because of an error in line 4.

Compilation fails because of an error in line 5.

The code creates an anonymous inner class that implements the TestA interface and overrides the toString() method to return "test". The code then creates an instance of this anonymous inner class and prints it using System.out.println(). Therefore, the output will be "test".

Explanation

The code creates an anonymous inner class that implements the TestA interface and overrides the toString() method to return "test". The code then creates an instance of this anonymous inner class and prints it using System.out.println(). Therefore, the output will be "test".

5.

Question 21
Given:
11. public abstract class Shape {
12. int x;
13. int y;
14. public abstract void draw();
15. public void setAnchor(int x, int y) {
16. this.x = x;
17. this.y = y;
18. }
19. }
and a class Circle that extends and fully implements the Shape class.
Which is correct?

Shape s = new Shape();s.setAnchor(10,10);s.draw();

Circle c = new Shape();c.setAnchor(10,10);c.draw();

Shape s = new Circle();s.setAnchor(10,10);s.draw();

Shape s = new Circle();s->setAnchor(10,10);s->draw();

Circle c = new Circle();c.Shape.setAnchor(10,10);c.Shape.draw();

not-available-via-ai

Explanation

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6. Which Man class properly represents the relationship "Man has a best friend who is a Dog"?

Class Man extends Dog { }

Class Man implements Dog { }

Class Man { private BestFriend dog; }

Class Man { private Dog bestFriend; }

Class Man { private Dog }

Class Man { private BestFriend }

The correct answer is "class Man { private Dog bestFriend; }". This answer represents the relationship "Man has a best friend who is a Dog" by declaring a private variable named "bestFriend" of type Dog within the Man class. This allows an instance of the Man class to have a reference to a Dog object, representing the association between a Man and their best friend who is a Dog.

Explanation

The correct answer is "class Man { private Dog bestFriend; }". This answer represents the relationship "Man has a best friend who is a Dog" by declaring a private variable named "bestFriend" of type Dog within the Man class. This allows an instance of the Man class to have a reference to a Dog object, representing the association between a Man and their best friend who is a Dog.

7.

Given:
1. public interface A {
2. String DEFAULT_GREETING = "Hello World";
3. public void method1();
4. }
A programmer wants to create an interface called B that has A as its
parent. Which interface declaration is correct?

Public interface B extends A { }

Public interface B implements A {}

Public interface B instanceOf A {}

Public interface B inheritsFrom A { }

The correct answer is "public interface B extends A { }". In Java, interfaces are implemented using the "implements" keyword, but when one interface extends another interface, the "extends" keyword is used. Therefore, to create an interface B that has A as its parent, the correct syntax is "public interface B extends A { }".

Explanation

The correct answer is "public interface B extends A { }". In Java, interfaces are implemented using the "implements" keyword, but when one interface extends another interface, the "extends" keyword is used. Therefore, to create an interface B that has A as its parent, the correct syntax is "public interface B extends A { }".

8.

Given:
11. public class Person {
12. private name;
13. public Person(String name) {
14. this.name = name;
15. }
16. public int hashCode() {
17. return 420;
18. }
19. }
Which is true?

The time to find the value from HashMap with a Person key dependson the size of the map.

Deleting a Person key from a HashMap will delete all map entries forall keys of type Person.

Inserting a second Person object into a HashSet will cause the firstPerson object to be removed as a duplicate.

The time to find the value from a HashMap with a Person key depends on the size of the map because the HashMap uses the hashCode() method of the Person class to calculate the index where the value is stored. If the map is larger, there may be more collisions and it may take longer to find the value.

Explanation

The time to find the value from a HashMap with a Person key depends on the size of the map because the HashMap uses the hashCode() method of the Person class to calculate the index where the value is stored. If the map is larger, there may be more collisions and it may take longer to find the value.

9.

Given:
11. public interface Status {
12. /* insert code here */ int MY_VALUE = 10;
13. }
Which three are valid on line 12? (Choose three.)

Final

Static

Native

Public

Private

Abstract

Protected

The three valid options for line 12 are "final", "static", and "public". "final" indicates that the value of MY_VALUE cannot be changed once it is assigned. "static" means that the variable belongs to the class itself, rather than to any particular instance of the class. "public" allows the variable to be accessed from other classes.

Explanation

The three valid options for line 12 are "final", "static", and "public". "final" indicates that the value of MY_VALUE cannot be changed once it is assigned. "static" means that the variable belongs to the class itself, rather than to any particular instance of the class. "public" allows the variable to be accessed from other classes.

Submit

10.

Given:
11. public class Test {
12. public static void main(String [] args) {
13. int x =5;
14. boolean b1 = true;
15. boolean b2 = false;
16.
17.if((x==4) && !b2)
18. System.out.print("l ");
19. System.out.print("2 ");
20. if ((b2 = true) && b1)
21. System.out.print("3 ");
22. }
23. }
What is the result?

2

3

1 2

2 3

1 2 3

Compilation fails.

Au exceptional is thrown at runtime.

The code snippet first checks if `x` is equal to 4 and `b2` is false. Since `x` is not equal to 4 and `b2` is false, the condition evaluates to false and the code inside the if statement on line 17 is not executed. Then, the code assigns `true` to `b2` and checks if `b2` is true and `b1` is true. Since both `b2` and `b1` are true, the condition evaluates to true and the code inside the if statement on line 20 is executed, which prints "3". Therefore, the result is "2 3".

Explanation

The code snippet first checks if `x` is equal to 4 and `b2` is false. Since `x` is not equal to 4 and `b2` is false, the condition evaluates to false and the code inside the if statement on line 17 is not executed. Then, the code assigns `true` to `b2` and checks if `b2` is true and `b1` is true. Since both `b2` and `b1` are true, the condition evaluates to true and the code inside the if statement on line 20 is executed, which prints "3". Therefore, the result is "2 3".

11.

Given:
10. public class Bar {
11.static void foo(int...x) {
12. // insert code here
13. }
14. }
Which two code fragments, inserted independently at line 12, will allow
the class to compile? (Choose two.)

Foreach(x) System.out.println(z);

For(int z : x) System.out.println(z);

While( x.hasNext()) System.out.println( x.next());

For( int i=0; i< x.length; i++ ) System.out.println(x[i]);

The two code fragments, "for(int z : x) System.out.println(z);" and "for( int i=0; i

Explanation

The two code fragments, "for(int z : x) System.out.println(z);" and "for( int i=0; i

Submit

12.

Given:
1. class TestA {
2. public void start() { System.out.println("TestA"); }
3. }
4. public class TestB extends TestA {
5. public void start() { System.out.println("TestB"); }
6. public static void main(String[] args) {
7. ((TestA)new TestB()).start();
8. }
9. }
What is the result?

TestA

TestB

Compilation fails.

An exception is thrown at runtime.

The code creates a new instance of TestB and then casts it to type TestA. The start() method is then called on this instance. Since the start() method is overridden in TestB, the version of the method in TestB is called. Therefore, the output will be "TestB".

Explanation

The code creates a new instance of TestB and then casts it to type TestA. The start() method is then called on this instance. Since the start() method is overridden in TestB, the version of the method in TestB is called. Therefore, the output will be "TestB".

13.

Given:
10. abstract public class Employee {
11. protected abstract double getSalesAmount();
12. public double getCommision() {
13. return getSalesAmount() * 0.15;
14. }
15. }
16. class Sales extends Employee {
17. // insert method here
18. }
Which two methods, inserted independently at line 17, correctly
complete the Sales class? (Choose two.)
.

Double getSalesAmount() { return 1230.45; }

Public double getSalesAmount() { return 1230.45; }

Private double getSalesAmount() { return 1230.45; }

Protected double getSalesAmount() { return 1230.45; }

The Sales class is extending the Employee class, which is an abstract class. In order to complete the Sales class, it needs to implement the abstract method getSalesAmount(). The correct methods to insert at line 17 are public double getSalesAmount() { return 1230.45; } and protected double getSalesAmount() { return 1230.45; }. These methods provide the implementation for the abstract method in the Employee class, allowing the Sales class to be instantiated and used.

Explanation

The Sales class is extending the Employee class, which is an abstract class. In order to complete the Sales class, it needs to implement the abstract method getSalesAmount(). The correct methods to insert at line 17 are public double getSalesAmount() { return 1230.45; } and protected double getSalesAmount() { return 1230.45; }. These methods provide the implementation for the abstract method in the Employee class, allowing the Sales class to be instantiated and used.

Submit

14.

12. Given:
13. public class Pass {
14. public static void main(String [1 args) {
15. int x 5;
16. Pass p = new Pass();
17. p.doStuff(x);
18. System.out.print(" main x = "+ x);
19. }
20.
21. void doStuff(int x) {
22. System.out.print(" doStuff x = "+ x++);
23. }
24. }
What is the result?

Compilation fails.

An exception is thrown at runtime.

DoStuffx = 6 main x = 6

DoStuffx = 5 main x = 5

DoStuffx = 5 main x = 6

DoStuffx = 6 main x = 5

The code will compile and run without any errors. The main method creates a variable "x" and assigns it a value of 5. Then, an instance of the Pass class is created and the doStuff method is called with the variable "x" as an argument. Inside the doStuff method, the value of "x" is printed and then incremented by 1. The main method then prints the value of "x" again. Since the increment operation in the doStuff method does not affect the value of "x" in the main method, the final output will be "doStuff x = 5 main x = 5".

Explanation

The code will compile and run without any errors. The main method creates a variable "x" and assigns it a value of 5. Then, an instance of the Pass class is created and the doStuff method is called with the variable "x" as an argument. Inside the doStuff method, the value of "x" is printed and then incremented by 1. The main method then prints the value of "x" again. Since the increment operation in the doStuff method does not affect the value of "x" in the main method, the final output will be "doStuff x = 5 main x = 5".

15.

Given:
10. interface Foo { int bar(); }
11. public class Sprite {
12. public int fubar( Foo foo) { return foo.bar(); }
13. public void testFoo() {
14. fubar(
15. // insert code here
16.);
17. }
18. }
Which code, inserted at line 15, allows the class Sprite to compile?

Foo { public int bar() { return 1; } }

New Foo { public int bar() { return 1; } }

NewFoo() { public int bar(){return 1; } }

New class Foo { public int bar() { return 1; } }

The correct answer is "newFoo() { public int bar(){return 1; } }". This code creates a new anonymous class that implements the Foo interface and defines the bar() method to return 1. This allows the class Sprite to compile because it can now pass an instance of this anonymous class to the fubar() method.

Explanation

The correct answer is "newFoo() { public int bar(){return 1; } }". This code creates a new anonymous class that implements the Foo interface and defines the bar() method to return 1. This allows the class Sprite to compile because it can now pass an instance of this anonymous class to the fubar() method.

16.

4. Given:
31. // some code here
32. try {
33. // some code here
34. } catch (SomeException se) {
35. // some code here
36. } finally {
37. // some code here
38. }
Under which three circumstances will the code on line 37 be executed?
(Choose three.)

The instance gets garbage collected.

The code on line 33 throws an exception.

The code on line 35 throws an exception.

The code on line 31 throws an exception.

The code on line 33 executes successfully.

The code on line 37 will be executed under the following three circumstances:
1. The code on line 33 throws an exception.
2. The code on line 35 throws an exception.
3. The code on line 33 executes successfully.

Explanation

The code on line 37 will be executed under the following three circumstances:
1. The code on line 33 throws an exception.
2. The code on line 35 throws an exception.
3. The code on line 33 executes successfully.

Submit

17.

Given:
23. Object [] myObjects = {
24. new integer(12),
25. new String("foo"),
26. new integer(5),
27. new Boolean(true)
28. };
29. Arrays.sort(myObjects);
30. for( int i=0; i

31. System.out.print(myObjects[i].toString());
32. System.out.print(" ");
33. }
What is the result?

Compilation fails due to an error in line 23.

Compilation fails due to an error in line 29.

A ClassCastException occurs in line 29.

A ClassCastException occurs in line 31.

The value of all four objects prints in natural order.

The code is attempting to sort an array of objects using the Arrays.sort() method. However, this method requires that the objects in the array implement the Comparable interface in order to determine their natural order. Since the array contains objects of different types (Integer, String, and Boolean), which do not implement Comparable, a ClassCastException occurs when trying to compare them during the sorting process. Therefore, the correct answer is that a ClassCastException occurs in line 29.

Explanation

The code is attempting to sort an array of objects using the Arrays.sort() method. However, this method requires that the objects in the array implement the Comparable interface in order to determine their natural order. Since the array contains objects of different types (Integer, String, and Boolean), which do not implement Comparable, a ClassCastException occurs when trying to compare them during the sorting process. Therefore, the correct answer is that a ClassCastException occurs in line 29.

18.

Given:
• d is a valid, non-null Date object
• df is a valid, non-null DateFormat object set to the
current locale
What outputs the current locales country name and the appropriate
version of d's date?

Locale loc = Locale.getLocale();System.out.println(loc.getDisplayCountry()+ “ “+ df.format(d));

Locale loc = Locale.getDefault();System.out.println(loc.getDisplayCountry()+ “ “ + df.format(d));

Locale bc = Locale.getLocale();System.out.println(loc.getDisplayCountry()+ “ “+ df.setDateFormat(d));

Locale loc = Locale.getDefault();System.out.println(loc.getDispbayCountry()+ “ “+ df.setDateFormat(d));

The correct answer is `Locale loc = Locale.getDefault(); System.out.println(loc.getDisplayCountry() + " " + df.format(d));`. This code retrieves the default locale and uses it to get the display country name using `loc.getDisplayCountry()`. It then formats the date `d` using the DateFormat object `df.format(d)`. Finally, it prints the country name and the formatted date.

Explanation

The correct answer is `Locale loc = Locale.getDefault(); System.out.println(loc.getDisplayCountry() + " " + df.format(d));`. This code retrieves the default locale and uses it to get the display country name using `loc.getDisplayCountry()`. It then formats the date `d` using the DateFormat object `df.format(d)`. Finally, it prints the country name and the formatted date.

19.

Given:
10. interface Data { public void load(); }
11. abstract class Info { public abstract void load(); }
Which class correctly uses the Data interface and Info class?
A

Public class Employee extends Info implements Data {public void load() { /*do something*/ }}

S

Public class Employee implements Info extends Data {public void load() { /*do something */ }public void Info.load(){ /*do something*/ }}

. public class Employee extends Info implements Data{public void Data.load() { /*do something*/ }public void Info.load() { /*do something*/ }}

The correct answer is option A because it correctly implements the Data interface and extends the Info class. The load() method is implemented in the Employee class, satisfying the requirements of both the interface and the abstract class.

Explanation

The correct answer is option A because it correctly implements the Data interface and extends the Info class. The load() method is implemented in the Employee class, satisfying the requirements of both the interface and the abstract class.

20. Which two classes correctly implement both the java.lang.Runnable and the java.lang.Clonable interfaces? (Choose two.)

Public class Sessionimplements Runnable, Clonable {public void run();public Object clone();}

The correct answers are:

1. public class Session implements Runnable, Clonable {
public void run() { / do something */ }
public Object clone() { /* make a copy */ }
}

2. public abstract class Session implements Runnable, Clonable {
public void run() { / do something */ }
public Object clone() { /*make a copy */ }

These two classes correctly implement both the java.lang.Runnable and the java.lang.Clonable interfaces because they provide the required methods for both interfaces: "run()" for the Runnable interface and "clone()" for the Clonable interface.

Explanation

The correct answers are:

1. public class Session implements Runnable, Clonable {
public void run() { / do something */ }
public Object clone() { /* make a copy */ }
}

2. public abstract class Session implements Runnable, Clonable {
public void run() { / do something */ }
public Object clone() { /*make a copy */ }

These two classes correctly implement both the java.lang.Runnable and the java.lang.Clonable interfaces because they provide the required methods for both interfaces: "run()" for the Runnable interface and "clone()" for the Clonable interface.

Submit

21.

Given:
11. public abstract class Shape {
12. private int x;
13. private int y;
14. public abstract void draw();
15. public void setAnchor(int x, int y) {
16. this.x = x;
17. this.y = y;
18. }
19. }
Which two classes use the Shape class correctly? (Choose two.)

Public class Circle implements Shape {private int radius;}

Public abstract class Circle extends Shape {private int radius;}

Public class Circle extends Shape {private int radius;public void draw();}

Blic abstract class Circle implements Shape {private int radius;public void draw();}

Public class Circle extends Shape {private int radius;public void draw() {/* code here */}}

Public abstract class Circle implements Shape {private int radius;public void draw() { / code here */ }}

The first class, "public abstract class Circle extends Shape", correctly uses the Shape class by extending it and implementing the abstract method "draw()". The second class, "public class Circle extends Shape", also correctly uses the Shape class by extending it and providing an implementation for the abstract method "draw()".

Explanation

The first class, "public abstract class Circle extends Shape", correctly uses the Shape class by extending it and implementing the abstract method "draw()". The second class, "public class Circle extends Shape", also correctly uses the Shape class by extending it and providing an implementation for the abstract method "draw()".

Submit

22.

Assume that country is set for each class.
Given:
10. public class Money {
11. private String country, name;
12. public getCountry() { return country; }
13.}
and:
24. class Yen extends Money {
25. public String getCountry() { return super.country; }
26. }
27.
28. class Euro extends Money {
29. public String getCountry(String timeZone) {
30. return super.getCountry();
31. }
32. }
Which two are correct? (Choose two.)

Yen returns correct values.

Euro returns correct values.

An exception is thrown at runtime.

Yen and Euro both return correct values.

Compilation fails because of an error at line 25.

Compilation fails because of an error at line 30.

The explanation for the correct answer is that Euro returns correct values because it overrides the getCountry() method from the superclass Money and returns the value of super.getCountry(). However, compilation fails because of an error at line 25 because the access modifier of the country variable in the superclass Money is private, so it cannot be accessed directly in the subclass Yen.

Explanation

The explanation for the correct answer is that Euro returns correct values because it overrides the getCountry() method from the superclass Money and returns the value of super.getCountry(). However, compilation fails because of an error at line 25 because the access modifier of the country variable in the superclass Money is private, so it cannot be accessed directly in the subclass Yen.

Submit

23.

Click the Exhibit button.
10. interface Foo {
11. int bar();
12. }
13.
14. public class Beta {
15.
16. class A implements Foo {
17. public int bar() { return 1; }
18. }
19.
20. public int fubar( Foo foo) { return foo.bar(); }
21.
22. public void testFoo() {
23.
24. class A implements Foo {
25. public int bar() { return 2; }
26. }
27.
28. System.out.println( fubar( new A()));
29. }
30.
31. public static void main( String[] argv) {
32. new Beta().testFoo();
33. }
34. }
Which three statements are true? (Choose three.)

Compilation fails.

The code compiles and the output is 2.

If lines 16, 17 and 18 were removed, compilation would fail.

If lines 24, 25 and 26 were removed, compilation would fail.

If lines 16, 17 and 18 were removed, the code would compile andthe output would be 2.

If lines 24, 25 and 26 were removed, the code would compile andthe output would be 1.

The code compiles and the output is 2 because the testFoo() method creates a new instance of the inner class A and calls the fubar() method with that instance. Since the inner class A implements the Foo interface and overrides the bar() method to return 2, the output will be 2. If lines 16, 17, and 18 were removed, the code would still compile and the output would be 2 because the inner class A would still be used. If lines 24, 25, and 26 were removed, the code would compile and the output would be 1 because the outer class A would be used, which returns 1 in the bar() method.

Explanation

The code compiles and the output is 2 because the testFoo() method creates a new instance of the inner class A and calls the fubar() method with that instance. Since the inner class A implements the Foo interface and overrides the bar() method to return 2, the output will be 2. If lines 16, 17, and 18 were removed, the code would still compile and the output would be 2 because the inner class A would still be used. If lines 24, 25, and 26 were removed, the code would compile and the output would be 1 because the outer class A would be used, which returns 1 in the bar() method.

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24.

Given:
10. package com.sun.scjp;
11. public class Geodetics {
12. public static final double DIAMETER = 12756.32; // kilometers
13. }
Which two correctly access the DIAMETER member of the Geodetics
class? (Choose two.)

Import com.sun.scjp.Geodetics;public class TerraCarta {public double halfway(){ return Geodetics.DIAMETER/2.0; } }

Import static com.sun.scjp.Geodetics;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

Import static com.sun.scjp.Geodetics. *;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

Package com.sun.scjp;public class TerraCarta {public double halfway() { return DIAMETER/2.0; } }

The correct answers are the first and fourth options.

In the first option, the Geodetics class is imported using the import statement, allowing direct access to the DIAMETER member using the class name.

In the fourth option, the Geodetics class is accessed using the fully qualified name, com.sun.scjp.Geodetics, allowing direct access to the DIAMETER member.

The second and third options are incorrect because they either do not import the Geodetics class or do not access the DIAMETER member correctly.

Explanation

The correct answers are the first and fourth options.

In the first option, the Geodetics class is imported using the import statement, allowing direct access to the DIAMETER member using the class name.

In the fourth option, the Geodetics class is accessed using the fully qualified name, com.sun.scjp.Geodetics, allowing direct access to the DIAMETER member.

The second and third options are incorrect because they either do not import the Geodetics class or do not access the DIAMETER member correctly.

Submit

25.