AP Computer Science Unit 2 - Test Review Practice Questions

Last Updated on August 9, 2024

AP Computer Science Unit 2—Test Review Practice Questions. AP Computer Science Principles (CSP) Unit 2: Using Objects Review Practice Test 2024: College Board’s Advanced Placement® Program (AP®) Computer Science Principles (CSP) Unit 2: The exam includes reference data to represent real-world objects in a digital world and discover methods to perform more complex operations.

In Unit 2, “Using Objects,” you focus on understanding and using objects and classes to model real-world entities and perform operations. This involves working with attributes, methods, constructors, and leveraging class libraries.

AP Computer Science Unit 2 – Test Review Practice Questions

AP Computer Science Unit 2 - Practice Questions

AP Computer Science Unit 2
Test Review Practice Questions
On The Exam: 5%–7.5% of exam score

1 / 20

Questions 1–3 refer to the Time class declared below:

public class Time
{
private int hrs;
private int mins;
private int secs;
public Time()
{ /* implementation not shown */ }
public Time(int h, int m, int s)
{ /* implementation not shown */ }
/** Resets time to hrs = h, mins = m, secs = s. */
public void resetTime(int h, int m, int s)
{ /* implementation not shown */ }
/** Advances time by one second. */
public void increment()
{ /* implementation not shown */ }
/** @return true if this time equals t, false otherwise */
public boolean equals(Time t)
{ /* implementation not shown */ }
/** @return true if this time is earlier than t, false otherwise */
public boolean lessThan(Time t)
{ /* implementation not shown */ }
/** @return a String with the time in the form hrs:mins:secs */
public String toString()
{ /* implementation not shown */ }
}

Which of the following is a false statement about the methods?

(A) equals, lessThan, and toString are all accessor methods.

(B) increment is a mutator method.

(D) The Time class has three constructors.

(E) There are no static methods in this class.

2 / 20

Questions 1–3 refer to the Time class declared below:

Which of the following represents correct implementation code for the constructor with parameters?

(A) hrs = 0; mins = 0; secs = 0;

(B) hrs = h; mins = m; secs = s;

(D) h = hrs; m = mins; s = secs;

(E) Time = new Time(h, m, s);

3 / 20

Questions 1–3 refer to the Time class declared below:

A client class has a display method that writes the time represented by its parameter:

/** Outputs time t in the form hrs:mins:secs.
* @param t the time
*/
public void display(Time t)
{
/* method body */
}

Which of the following are correct replacements for / method body /?

I Time T = new Time(h, m, s); System.out.println(T);
II System.out.println(t.hrs + ":" + t.mins + ":" + t.secs);
III System.out.println(t);

(A) I only

(B) II only

(D) II and III only

(E) I, II, and III

4 / 20

Which statement about parameters is false?

(A) The scope of parameters is the method in which they are defined.

(B) Static methods have no implicit parameter this.

(D) All parameters in Java are passed by value.

(E) Two different constructors in a given class can have the same number of parameters.

5 / 20

Questions 5–11 refer to the following Date class declaration:

public class Date
{
private int day;
private int month;
private int year;
public Date() //default constructor
{
...
}
public Date(int mo, int da, int yr) //constructor
{
...
}
public int month() //returns month of Date
{
...
}
public int day() //returns day of Date
{
...
}
public int year() //returns year of Date
{
...
}
//Returns String representation of Date as "m/d/y", e.g. 4/18/1985.
public String toString()
{
...
}
}

Which of the following correctly constructs a Date object in a client class?

(A) Date d = new (2, 13, 1947);

(B) Date d = new Date(2, 13, 1947);

(D) Date d; d = Date(2, 13, 1947);

(E) Date d = Date(2, 13, 1947);

6 / 20

Questions 5–11 refer to the following Date class declaration:

Which of the following will cause an error message?

I Date d1 = new Date(8, 2, 1947); Date d2 = d1;
II Date d1 = null; Date d2 = d1;
III Date d = null; int x = d.year();

(A) I only

(B) II only

(D) II and III only

(E) I, II, and III

7 / 20

Questions 5–11 refer to the following Date class declaration:

A client program creates a Date object as follows:

Date d = new Date(1, 13, 2002);

Which of the following subsequent code segments will cause an error?

(A) String s = d.toString();

(B) int x = d.day();

(D) Date e = new Date(1, 13, 2002);

(E) int y = d.year;

8 / 20

Questions 5–11 refer to the following Date class declaration:

Consider the implementation of a write() method that is added to the Date class:

/** Write the date in the form m/d/y, for example 2/17/1948. */
public void write()
{
/* implementation code */
}

Which of the following could be used as / implementation code /?

I System.out.println(month + "/" + day + "/" + year);
II System.out.println(month() + "/" + day() + "/" + year());
III System.out.println(this);

(A) I only

(B) II only

(D) II and III only

(E) I, II, and III

9 / 20

Questions 5–11 refer to the following Date class declaration:

Here is a client program that uses Date objects:

public class BirthdayStuff { public static Date findBirthdate() { /* code to get birthDate */ return birthDate; } public static void main(String[] args) { Date d = findBirthdate(); ... } }

Which of the following is a correct replacement for / code to get birthDate /?

I System.out.println("Enter birthdate: mo, day, yr: "); int m = IO.readInt(); int d = IO.readInt(); int y = IO.readInt(); Date birthDate = new Date(m, d, y);
II System.out.println("Enter birthdate: mo, day, yr: "); int birthDate.month() = IO.readInt(); int birthDate.day() = IO.readInt(); int birthDate.year() = IO.readInt(); Date birthDate = new Date(birthDate.month(), birthDate.day(), birthDate.year());
III System.out.println("Enter birthdate: mo, day, yr: "); int birthDate.month = IO.readInt(); int birthDate.day = IO.readInt(); int birthDate.year = IO.readInt(); Date birthDate = new Date(birthDate.month, birthDate.day, birthDate.year);

(A) I only

(B) II only

(D) I and II only

(E) I and III only

10 / 20

Questions 5–11 refer to the following Date class declaration:

public class Date
{
private int day;
private int month;
private int year;
public Date() //default constructor
{
...
}
public Date(int mo, int da, int yr) //constructor
{
...
}
public int month() //returns month of Date
{
...
}
public int day() //returns day of Date
{
...
}
public int year() //returns year of Date
{
s
...
}
//Returns String representation of Date as "m/d/y", e.g. 4/18/1985.
public String toString()
{
...
}
}

A method in a client program for the Date class has this declaration:

Date d1 = new Date(mo, da, yr);

where mo, da, and yr are previously defined integer variables. The same method now creates a second Date object d2 that is an exact copy of the object d1 refers to. Which of the following code segments will not do this correctly?

I Date d2 = d1;
II Date d2 = new Date(mo, da, yr);
III Date d2 = new Date(d1.month(), d1.day(), d1.year());

(A) I only

(B) II only

(D) II and III only

(E) I, II, and III

11 / 20

Questions 5–11 refer to the following Date class declaration:

public class Date
{
private int day;
private int month;
private int year;
public Date() //default constructor
{
...
}
public Date(int mo, int da, int yr) //constructor
{
...
}
public int month() //returns month of Date
{
...
}
public int day() //returns day of Date
{
...
}
public int year() //returns year of Date
{
s
...
}
//Returns String representation of Date as "m/d/y", e.g. 4/18/1985.
public String toString()
{
...
}
}

The Date class is modified by adding the following mutator method:

public void addYears(int n) //add n years to date

Which will be true after executing this code?

public static void addCentury(Date recent, Date old)
{
old.addYears(100);
recent = old;
}
public static void main(String[] args)
{
Date oldDate = new Date(1, 13, 1900);
Date recentDate = null;
addCentury(recentDate, oldDate);
...
}

(A) A NullPointerException is thrown.

(B) The oldDate object remains unchanged.

(D) recentDate refers to the same object as oldDate.

(E) recentDate refers to a separate object whose contents are the same as those of oldDate.

12 / 20

Here are the private instance variables for a Frog object:

public class Frog
{
private String species;
private int age;
private double weight;
private Position position; //position (x,y) in pond
private boolean amAlive;
...
}

Which of the following methods in the Frog class is the best candidate for being a static method?

(A) swim //frog swims to new position in pond

(B) getPondTemperature //returns temperature of pond

(D) getWeight //returns weight of frog

(E) die //frog dies with some probability based on frog’s age and pond temperature

13 / 20

What output will be produced by this program?

public class Mystery
{
public static void strangeMethod(int x, int y)
{
x += y;
y *= x;
System.out.println(x + " " + y);
}
public static void main(String[] args)
{
int a = 6, b = 3;
strangeMethod(a, b);
System.out.println(a + " " + b);
}
}

(A) 36 9

(B) 3 6 9

(D) 6 3 9 27

(E) 9 27 6 3

14 / 20

Questions 14–17 refer to the following definition of the Rational class

public class Rational
{
private int numerator;
private int denominator;
/** default constructor */
Rational()
{ /* implementation not shown */ }
/** Constructs a Rational with numerator n and
* denominator 1. */
Rational(int n)
{ /* implementation not shown */ }
/** Constructs a Rational with specified numerator and
* denominator. */
Rational(int numer, int denom)
{ /* implementation not shown */ }
/** @return numerator */
int numerator()
{ /* implementation not shown */ }
/** @return denominator */
int denominator()
{ /* implementation not shown */ }
/** Returns (this + r). Leaves this unchanged.
* @return this rational number plus r
* @param r a rational number to be added to this Rational
*/
public Rational plus(Rational r)
{ /* implementation not shown */ }
//Similarly for times, minus, divide
...
/** Ensures denominator > 0. */
private void fixSigns()
{ /* implementation not shown */ }
/** Ensures lowest terms. */
private void reduce()
{ /* implementation not shown */ }
}

14. The method reduce() is not a public method because

(A) methods whose return type is void cannot be public.

(B) methods that change this cannot be public.

(D) the reduce() method is intended for use only by clients of the Rational class.

(E) the reduce() method uses only the private data fields of the Rational class.

15 / 20

Questions 14–17 refer to the following definition of the Rational class

15. The constructors in the Rational class allow initialization of Rational objects in several different ways. Which of the following will cause an error?

(A) Rational r1 = new Rational();

(B) Rational r2 = r1;

(D) Rational r4 = new Rational(3.5);

(E) Rational r5 = new Rational(10);

16 / 20

Questions 14–17 refer to the following definition of the Rational class

16. Here is the implementation code for the plus method:

/** Returns (this + r). Leaves this unchanged.
* @return this rational number plus r
* @param r a rational number to be added to this Rational
*/
public Rational plus(Rational r)
{
fixSigns();
r.fixSigns();
int denom = denominator * r.denominator;
int numer = numerator * r.denominator + r.numerator * denominator;
/* more code */
}

Which of the following is a correct replacement for / more code /?

(A) Rational rat(numer, denom); rat.reduce(); return rat;

(B) return new Rational(numer, denom);

(D) Rational rat = new Rational(numer, denom); Rational.reduce(); return rat;

(E) Rational rat = new Rational(numer, denom); rat.reduce(); return rat;

17 / 20

Questions 14–17 refer to the following definition of the Rational class

17. Assume these declarations:

Rational a = new Rational();
Rational r = new Rational(numer, denom);
int n = value;
//numer, denom, and value are valid integer values

Which of the following will cause a compile-time error?

(A) r = a.plus(r);

(B) a = r.plus(new Rational(n));

(D) a = n.plus(r);

(E) r = r.plus(new Rational(n));

18 / 20

Questions 18–20 refer to the Temperature class shown below

public class Temperature
{

private String scale; //valid values are "F" or "C"
private double degrees;
/** constructor with specified degrees and scale */
public Temperature(double tempDegrees, String tempScale)
{ /* implementation not shown */ }
/** Mutator. Converts this Temperature to degrees Fahrenheit.
* Precondition: Temperature is a valid temperature
* in degrees Celsius.
* @return this temperature in degrees Fahrenheit
*/
public Temperature toFahrenheit()
{ /* implementation not shown */ }
/** Mutator. Converts this Temperature to degrees Celsius.
* Precondition: Temperature is a valid temperature
* in degrees Fahrenheit.
* @return this temperature in degrees Celsius
*/
public Temperature toCelsius()
{ /* implementation not shown */ }
/** Mutator.
* @param amt the number of degrees to raise this temperature
* @return this temperature raised by amt degrees
*/
public Temperature raise(double amt)
{ /* implementation not shown */ }
/** Mutator.
* @param amt the number of degrees to lower this temperature
* @return this temperature lowered by amt degrees
*/
public Temperature lower(double amt)
{ /* implementation not shown */ }
/** @param tempDegrees the number of degrees
* @param tempScale the temperature scale
* @return true if tempDegrees is a valid temperature
* in the given temperature scale, false otherwise
*/
public static boolean isValidTemp(double tempDegrees,
String tempScale)
{ /* implementation not shown */ }
//Other methods are not shown.

}

18. A client method contains this code segment:

Temperature t1 = new Temperature(40, "C");
Temperature t2 = t1;
Temperature t3 = t2.lower(20);
Temperature t4 = t1.toFahrenheit();

Which statement is true following execution of this segment?

(A) t1, t2, t3, and t4 all represent the identical temperature, in degrees Celsius.

(B) t1, t2, t3, and t4 all represent the identical temperature, in degrees Fahrenheit.

(D) t1 and t2 refer to the same Temperature object; t3 refers to a Temperature object that is 20 degrees lower than t1 and t2, while t4 refers to an object that is t1 converted to Fahrenheit.

(E) A NullPointerException was thrown.

19 / 20

Questions 18–20 refer to the Temperature class shown below

public class Temperature
{

}

19. Consider the following code:

public class TempTest
{
public static void main(String[] args)
{
System.out.println("Enter temperature scale: ");
String tempScale = IO.readString(); //read user input
System.out.println("Enter number of degrees: ");
double tempDegrees = IO.readDouble(); //read user input
/* code to construct a valid temperature from user input */
}
}

Which is a correct replacement for / code to construct. . . /?

I Temperature t = new Temperature(tempDegrees, tempScale); if (!t.isValidTemp(tempDegrees,tempScale)) /* error message and exit program */
II if (isValidTemp(tempDegrees,tempScale)) Temperature t = new Temperature(tempDegrees, tempScale); else /* error message and exit program */
III if (Temperature.isValidTemp(tempDegrees,tempScale)) Temperature t = new Temperature(tempDegrees, tempScale); else /* error message and exit program */

(A) I only

(B) II only

(D) I and II only

(E) I and III only

20 / 20

Questions 18–20 refer to the Temperature class shown below

public class Temperature
{

}

20. The formula to convert degrees Celsius C to Fahrenheit F is F = 1.8C + 32. An inFahrenheit() accessor method is added to the Temperature class. Here is its implementation:

/** Precondition: The temperature is a valid temperature
* in degrees Celsius.
* Postcondition:
* - An equivalent temperature in degrees Fahrenheit has been
* returned.
* - Original temperature remains unchanged.
* @return an equivalent temperature in degrees Fahrenheit
*/
public Temperature inFahrenheit()
{
Temperature result;
/* more code */
return result;
}

Which of the following correctly replaces / more code / so that the postcondition is achieved?

result = new Temperature(degrees * 1.8 + 32, "F");
result = new Temperature(degrees * 1.8, "F"); result = result.raise(32);
degrees *= 1.8; this = this.raise(32); result = new Temperature(degrees, "F");

(A) I only

(B) II only

(D) I and II only

(E) I, II, and III

Your score is

Test Review Practice Questions

AP CSP Practice Test 2024 Study Guide [UPDATED]

Full Practice Test

AP CSP Practice Test 2021 Questions Answers [PDF]

Topics Overview

Objects and Classes

Objects: Instances of classes that represent real-world entities.
Classes: Blueprints for creating objects, defining attributes (fields) and behaviors (methods).
Attributes: Variables within a class that hold the state of an object.
Behaviors: Methods within a class that define what an object can do.

Creating Objects

Constructors: Special methods used to initialize objects.
Default Constructor: Initializes objects with default values.
Parameterized Constructor: Initializes objects with specified values.

Class Libraries

Integer and Double Classes: Wrapper classes for primitive data types.
Math Class: Provides methods for mathematical operations.
String Class: Manages and manipulates text data.

Methods

Non-Static Methods: Operate on instances of a class and can access instance variables.
Static Methods: Belong to the class itself rather than instances and can’t access instance variables.
Void Methods: Do not return a value.

String Objects and Methods

String Manipulation: Methods to handle text, such as length(), substring(), and toUpperCase().

APIs and Libraries

Using External Libraries: Integrating and utilizing predefined code to perform tasks.
Application Program Interfaces (APIs): Interfaces that allow interaction with other software components.