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When viewed as as a black box, an object presents the client with which of the following? Its public interface Its prime sieve Its object signature Its command-line arguments

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Mar 1, 2020

Cards (99)

Section 1

(50 cards)

When viewed as as a black box, an object presents the client with which of the following? Its public interface Its prime sieve Its object signature Its command-line arguments

Front

its public interface

Back

All methods of a class can access data declared at the class level (T or F)

Front

true

Back

Variables declared within a method cease to exist when the method returns control to the caller. True False

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true

Back

A constructor cannot be overloaded. True False

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false

Back

T/F: The main method accepts a variable-length argument list

Front

false

Back

In a JavaFX Polygon object, the last vertex point is automatically connected to the first. True False

Front

true

Back

Encapsulation ensures which of the following? A) that hackers cannot breach the data in an object B) that a class cannot be used to derive another class C) that a client is the same class as the object with which it communicates D) that an object is in charge of modifying the values of its data

Front

D

Back

The println method accepts a variable number of parameters.

Front

false

Back

Given the following code, which of the expressions is false? Point p1 = new Point(8, 12); Point p2 = new Point(8, 12); Point p3 = p2; p2.equals(p1) p1 == p2 p2 == p3 p3.equals(p1)

Front

p1 == p2

Back

T/F: The deposit method of the BankAccount class is a mutator method

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true

Back

The Java API is organized into what? A) Packages B) Groups C) Tuples D) Objects

Front

packages

Back

The minimum number of value is minimized to 1 and the maximum value is equal to the number of sides. What is the output of the following code? Die die = new Die(6); System.out.println("Die value: " + die);

Front

die value: 1

Back

T/F: Getter methods always return a String.

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false

Back

A getter method always returns an integer value. True False

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false

Back

Which of the following is NOT true about the this reference? It can be used to call a method from another class. It can be used to call a constructor. It can be used to explicitly refer to the object on which a method is called. It can be used to distinguish a parameter from instance data.

Front

it can be used to call a method from another class

Back

If the compiler finds two or more methods that equally match a given call, it will issue an error. This problem is called a(n)

Front

ambiguous invocation

Back

T/F: A bounds error will result in an exception being thrown

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true

Back

T/F: Two methods in the same class can have the same name

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true

Back

T/F: Constructors cannot be overloaded.

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false

Back

Caused when you try to access an array element that doesn't exist.

Front

bounds error

Back

The minimum number of value is minimized to 1 and the maximum value is equal to the number of sides. What is the output of the following code? Die die = new Die(20); die.roll(); die.roll(); System.out.println(die.getValue());

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# between 1 and 20

Back

Which of the following is NOT true about the this reference? A) it can be used to call a constructor B) it can be used to call a method from a parent class C) it can be used to distinguish a parameter from instance data D) it can be used to explicitly refer to the object on which a method is invoked

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B

Back

The state of an object is represented by what? The values of its instance data. The visibility modifiers used on its instance data. The methods in its public interface. The signatures of its method

Front

values of its instance data

Back

Which analogy is appropriate? A) a class is like a car and an object is like a truck B) an object is like a car and a class like a truck C)a class is like a blueprint and an object is like a house D) an object is like a blueprint and a class is like a house

Front

c

Back

Within a class, methods must have unique names. True False

Front

false

Back

Are numeric types signed?

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yes

Back

What is part of the method signature?

Front

name of the method and the type of its parameters; all method signatures must be unique

Back

What violates encapsulation?

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public variables and instance data

Back

T/F: The Java keyword this is an explicit reference to the object on which a method is invoked.

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true

Back

The return type of a constructor must be void (T or F)

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false

Back

What is the value of val after the following code segment is executed int val = 20; val *= 2; val = val + 5;

Front

45

Back

What does the this reference refer to? A) the object on which a method is invoked B) the object passed as the first parameter to a method C) the object returned by a method D) the parent object of the current object

Front

A

Back

T/F: The behavior of an object is determined by its public interface

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true

Back

T/F: The toString method is automatically called when an object is printed.

Front

true

Back

Computing an incorrect result is an example of what kind of error?

Front

logic

Back

T/F: If you call a method through a null reference the compiler will issue an error

Front

false

Back

What is the method signature of the method below? public void setCoordinates(int x, int y)

Front

setCoordinates(int, int)

Back

T/F: Both dimensions of a two-dimensional array must have the same element type

Front

true

Back

Suppose a method called checkPos was to return true if both of its parameters was positive, and false otherwise public checkPos (int a, int b) { return _; } What would go in the first and second blank respectfully?

Front

Boolean, a > 0 && b > 0

Back

An ellipses (...) is used to specify a method that accepts command-line arguments. True False

Front

false

Back

Each object has its own memory space for instance data (T or F)

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true

Back

Which of the following violates the principle of encapsulation? public constants private methods public methods public instance data

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public instance data

Back

Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.length() give?

Front

18 Length is the number of characters so last index + 1

Back

T/F: An array that holds objects cannot be created using initialization lists

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false

Back

Scaling a JavaFX Group object causes each element in the group to be scaled by the same amount. True False

Front

true

Back

When comparing String objects, on what does the compareTo method base its result? Character positions in the Unicode character set Demographic order String numeric values after non-alpha characters are removed Alphabetical order

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Character positions in the Unicode character set

Back

T/F: A class must have a getter and setter method for each instance variable.

Front

false

Back

Given the following declaration, which expression will extract the substring "show"? String phrase = "I could show you incredible things";

Front

phrase.substring(8, 12)

Back

Program options are often specified using what?

Front

command line arguments

Back

A JavaFX Arc is defined as a portion of what other shape? Circle Polyline Line Ellipse

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ellipse

Back

Section 2

(49 cards)

A two-dimensional array is really a one-dimensional array of one-dimensional arrays. True False

Front

true

Back

What are synonyms for the existing class, the superclass?

Front

parent class, base class

Back

The pattern from which an object is created.

Front

class

Back

What are synonyms for the new class, the subclass?

Front

child class, derived class

Back

It is possible to create an array with more than two dimensions. True False

Front

true

Back

What must the child of an abstract class provide in order not to be considered abstract also?

Front

provide definitions for the inherited abstract methods

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1 == p2, T/F?

Front

true

Back

An abstract class cannot be declared as final

Front

true - must derive classes from it

Back

What does this.radius=radius do?

Front

It assigns the parameter value to the instance data

Back

What's different about an overridden method in a subclass compared to the inherited version? different parameters but same method name and code same method name and parameters but different code different method name but the same code same method name and code but different return type

Front

same method name and parameters but different code

Back

If Lockable is an interface, which statement must be true given the following declaration? Lockable obj = new Book(); Lockable must define the methods in Book Book must contain Lockable Book must implement Lockable Lockable must implement the Book class

Front

book must implement lockable

Back

if (obj1.equals(obj2)) means?

Front

equivalent content

Back

If the ﬁnal modiﬁer is applied to a method, that method cannot be overridden in any derived class True/False

Front

true

Back

Which of the following statements is true? An interface can contain public and private methods. An interface can contain methods and classes. An interface can contain methods and constants. An interface can contain methods and instance variables.

Front

an interface can contain methods and constants

Back

Graphically and in code, from what to what do you read the is-a relationship ?

Front

Graphically: from the start of arrow to end of arrow In code: From right to left ex. Vehicle v; v= new Sedan(); A sedan IS A vehicle but a vehicle isn't always a sedan

Back

The instanceof operator determines if an object reference variable is currently pointing to an object of a particular type. True False

Front

true

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1 == p3, T/F?

Front

false

Back

Which line of code demonstrates a valid and error-free way to access the following array? String[][] chessboard = new String[8][8]; String chessPiece = chessboard[1][8]; String chessPiece = chessboard[1]; String chessPiece = chessboard["2"]["3"]; String chessPiece = chessboard[5][2]; String chessPiece = chessboard[4][];

Front

String chessPiece = chessboard[5][2]; * in bounds

Back

How many elements can be stored in a two-dimensional array with dimensions 5 and 10?

Front

50

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1 == p4, T/F?

Front

false

Back

If a class is not explicitly derived from a particular class, where is it derived from?

Front

the object class

Back

The maximum indexes of a two-dimensional array with 6 rows and 10 columns are 5 and 9, respectively. True False

Front

true

Back

The data managed by an object.

Front

instance data

Back

A Java interface defines which of the following? system interface keyword interface printable interface user interface

Front

system interface

Back

An abstract class can instantiated True/False

Front

false

Back

Every class can only have one parent. True/False

Front

true

Back

How does the default version of the equals method act if not overridden?

Front

Acts as the == operator, so returns true if two references point to the same object

Back

When a method is invoked, what determines which is invoked?

Front

The type of the object NOT the type of reference

Back

What Java keyword is used to create a subclass? interface implements extends inherits

Front

extends

Back

How can it be determined what type of objects an object reference can refer to?

Front

Distinguish between the object reference type and the type of object (class) it refers to

Back

What is the difference between method overloading and overriding

Front

Method overloading is when two or more Java methods in the same class have the same name but as long as have different parameters; Overriding is when a method from the parent class is defined again in the sub class (overriding the inherited version) with own version

Back

What's an abstract class?

Front

is a placeholder in a class hierarchy that represents a general concept

Back

What is the ultimate root of every class hierarchy?

Front

java.lang.Object class

Back

A Java interface cannot be instantiated. True False

Front

true ** can only create methods in an interface

Back

Methods and data declared as protected can be accessed from any derived class True/False

Front

true

Back

A class can only implement one interface at a time. True False

Front

false

Back

What are abstract methods?

Front

method headers with no bodies

Back

Assuming the table is a two-dimensional array of integers, what does the following code do? int sum = 0; for (int i = 0; i < table.length; i++) for (int j = 0; j < table[i].length; j++) sum = sum + table[i][j]; Computes the sum of each column in the table. Computes the sum of all elements in the table except those in the last column. Computes the sum of all elements in the table except those in the last row. Computes the sum of each row in the table. Computes the sum of all values in the table.

Front

computes the sum of all values in the table

Back

An abstract can only contain abstract methods True/False

Front

false

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1.equals(p4), T/F?

Front

false

Back

An integer can equal a double True/False

Front

false * only double can equal integer

Back

What can an object reference variable refer/point to?

Front

Any object of it's type or any type derived from it ex. A car reference could point to a car object or sedan or suv object but NOT vice-versa Car automobile; automobile = new Car(); automobile = new Sedan(); automobile = new SUV();

Back

What is the role of the seed value of a random number generator? It's the maximum number of values that can be produced by the generator. It's the maximum value that can be generated by that object. It's a number that is the basis of the calculated pseudorandom numbers. It's the minimum value of any range produced by the generator.

Front

It's a number that is the basis of the calculated pseudorandom numbers.

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1.equals(p2), T/F?

Front

true

Back

If the ﬁnal modiﬁer is applied to a class, that class cannot be used to derive a subclass True/False

Front

true

Back

Point p1 = new Point(4, 7); Point p2 = p1; Point p3 = new Point(4, 7); Point p4 = new Point(5, 12); p1.equals(p3), T/F?

Front

true

Back

Defines the code that is executed when a method is called.

Front

method declaration

Back

if (obj1 == obj2) means?

Front

point to the same object (reference equality)

Back

Private data and methods cannot be accessed by name in a derived class True/False

Front

true

Back