IS 247 Midterm

Which statement best reflects a property or characteristic of a constructor?

has the same name as the class

Suppose we have a String object referenced by a variable called listing. Suppose we want a new String object that consists of the first 5 characters in listing. Which of the following lines of code will achieve this?

String prefix = listing.substring(0,5);

Do constructors have a return type?

false

Static member functions can only access member variables that are also static.

True

A constructor is a method that __________. Choose the best answer.

performs creation, initialization or setup of an object

A constructor is invoked to create an object using the ________ operator.

new

Get methods are also called ___________ type methods.

accessor

How are instance member and static member variables different?

only one instance of a static variable exists in memory

When does a static member variable come into existence in memory?

before any instances of its class

Set methods are also called ___________ type methods.

mutator

Which method returns the number of characters stored in StringBuilder?

length()

Class abstraction separates class implementation from the use of the class.

true

When a method has the same name as another method but different parameters, it is referred to as ______________________

overloaded

Given the declaration Circle x = new Circle(), which of the following statement is most accurate.

x contains a reference to a Circle object

For the following String:

String str = "ABcdeFGH";

What will be returned from the following statements?

Character.toUpperCase(str.charAt(3));

Character.toUpperCase(str.charAt(5));

DE

Which of the following method headers is most likely a header for a mutator method?

public void setAge(int newAge)

Converting a primitive or class in Java into other type is called ______________.

casting

A super class can be derived from another class.

true

Suppose we have a String object referenced by a variable called listing. Suppose we want a new String object that consists of the first 5 characters in listing. Which of the following lines of code will achieve this?

String prefix = listing.substring(0,5);

Another term for an object of a class is a(n) __________.

instance

Which operator is used to access a data field or invoke a method from an object?

the dot operator

This keyword is means that a variable is not able to be modified once it is initialized.

final

Suppose we have a String object referenced by a variable called listing. Suppose we want a new String object that consists of the first 5 characters in listing. Which of the following lines of code will achieve this?

String prefix = listing.substring(0,5);

Given the declaration Circle[] x = new Circle[10], which of the following statement is most accurate?

x contains a reference to an array and each element in the array can hold a reference to a Circle object.

Get methods are also called ___________ type methods.

accessor

A method that has multiple definitions distinguished by the parameter number or type is an __________________ method.

overloaded

Which access specifier is most appropriate to implement encapsulation?

private

instances of wrapper classes are immutable.

true

A constructor with only one parameter is the "default" constructor.

false

Which method returns the number of characters stored in StringBuilder?

length()

A ___________ variable represents information or data shared by all objects of the class.

static

The "this" pointer is passed to a static member function.

false

Converting a primitive or class in Java into other type is called ______________.

casting

Suppose that Horse is a subclass of Animal, and neither class is abstract. Which of the following is an invalid declaration and initialization?

Horse h = new Animal();

Which class can you use to write data into a text file?

PrintWriter

To catch an exception, the code that might have an error must be enclosed in a ________________ block.

try

"try-with-resources" syntax is used to ___________________.

automatically close the files used in the program.

A(n) _____________________ is an object that defines an erroneous situation from which the program usually cannot recover.

error

A finally clause is always required in a try-catch block.

false

To handle an exception that has been thrown, a program must have a(n) ____________________

try/catch block

What does the following statement do?

Scanner scanner = new Scanner(Paths.get("test.txt"));

Opens a text file for input.

All exception classes inherit, either directly or indirectly, from ________.

class Throwable.

If the data.dat file already exists, what will happen when the following statement is executed?

FileWriter fwriter = new FileWriter("data.dat");

The file will be erased and replaced with the new file

Files that are open for output from a program must be explicitly closed in the program.

true

Which of the following exceptions is a checked exception?

IOException.

Which method can be used to read a whole line from the file?

nextLine

In a try/catch construct, after the catch statement is executed __________.

the program resumes at the statement that immediately follows the try/catch construct

A(n) ____________________ is used to specify how certain exceptions should be handled.

catch block

An uncaught exception ________.

is an exception that occurs for which there are no matching catch clauses.

What is the java root class for exceptions?

java.lang.Throwable

Which class contains the method for checking whether a file exists?

File

Which of the following statements regarding abstract classes and methods is FALSE?

A data field can be declared abstract.

Which keyword is used when requiring an interface for a class?

implements

Which of the following statements is correct?

An abstract class may contains constructors.

Which statement best reflects the definition of a Java interface?

a collection of abstract methods and constants

Which of the following statements regarding abstract methods is false?

A data field can be declared abstract.

A subclass can implement multiple interfaces.

true

Class abstraction separates class implementation from the use of the class.

true

Which of the following statements regarding abstract methods is FALSE?

An abstract class can have instances created using the constructor of the abstract class.

What is an abstract method?

A method which is not implemented.

If Person is an interface. Then it is possible to create an object by instantiating the Person interface.

false

Of the classes below, the one that is most likely to be declared abstract is _________________.

a) dog

b) cat

c) animal

d) horse

animal

Which of these access specifiers is most appropriate to use for an interface?

public

How many base cases must a recursive method have?

at least one

What is wrong with the following recursive method that computes the sum of all of the odd positive integers less than or equal to n?

public int sumOfOdds(int n)

{

if(n%2 == 0)

return sumOfOdds(n-1);

else

return n + sumOfOdds(n-2);

}

a) there are two base cases

b) adds both even and odd

c) no base case

d) recursive values don't decrement correctly

no base case

All mathematical problems are designed to be more efficient using recursive solutions.

false

Which type of recursion is more difficult to debug?

indirect

A problem can be solved recursively if it can be broken down into successive smaller problems that are identical to the overall problem.

true

Without a base case, a recursive method will call itself only once and stop.

false

____________________ recursion occurs when a method calls itself, while _________________ recursion when a method calls another method that then calls the original method.

a) upward, downward

b) downward, upward

c) direct, indirect

d) indirect, direct

direct, indirect

Recursive solutions are always more efficient than iterative solutions

false

In the following code that uses recursion to find the greatest common divisor of a number, what is the base case?

public static int gcd(int x, int y)

{

if (x % y == 0)

return y;

else

return gcd(y, x % y);

}

a) gcd(int x, int y)

b) if (x % y == 0)

return y;

c) else

return gcd(y, x % y);

d) cannot tell from this code

if (x % y == 0)

What is one of the benefits of recursion?

shorter code

A _____________________ method is one that calls itself.

recursive

25 % 5 is ______?

0

Which of the following is the correct statement to return JAVA?

a) String.toUpperCase("Java")

b) toUpperCase("Java")

c) "Java".toUpperCase()

d) "Java".toUpperCase("Java")

"Java".toUpperCase()

What is the index variable for the element at the second row and first column in array a?

a) a[0][1]

b) a[2][1]

c) a[1][0]

d) a[1][1]

a[1][0]

What is the exact output of the following code?

public class MyClass {

public static void main(String args[]) {

float num = 7.3f;

System.out.print("num");

System.out.print(num);

}

}

a) 7.3

b) num7.3f

c) num7.3

d) 7.37.3

num7.3

What is displayed in the following code?

public class Test {

public static void main(String[] args) {

int x = 1;

int y = x-- + x;

System.out.println("y is " + y);

}

}

a) y is 1

b) y is 4

c) y is 2

d) y is 3

y is 1

When you invoke a method with a parameter, the value of the argument is passed to the parameter. This is referred to as _________.

pass by value

Suppose x is 1. What is x after x += 1?

2

The __________ method returns a raised to the power of b.

a) Math.pow(b, a)

b) Math.pow(a, b)

c) Math.power(a, b)

d) Math.exponent(a, b)

Math.pow(a, b)

How many times will the following code print "Welcome to Java"?

int count = 0;

while (count

11

"abc".compareTo("aba") returns ___________.

a) -1

b) 2

c) -1

d) 1

2

How many elements are array matrix (int[][] matrix = new int[2][5])?

a) 20

b) 10

c) 25

d) 14

10

Which loop statement will execute the code before the loop condition is tested?

a) for each

b) for

c) while

d) do-while

do-while

An _____ object cannot be modified

immutable

the _____ clause is always executed regardless of wether an exception occurred or not

finally

the keyword _____ can be used to refer to its calling object. It can also be used inside a constructor ti invoke another constructor of the same class

this

_____ is a special form of association between classes that represents an ownership between objects

aggregation

the separation of class implementation from the use of a class is called class ______

abstraction

_____ means that a variable of a supertype can refer to a subtype object

polymorphism

a _____ is a template for objects

class

the keyword _____ can be used to invoke the superclass's methods and constructors

super

_____ means to define multiple methods with the same name but different signatures

overloading

_____ means ti provide a new implementation for a method in the subclass

overriding

_____ enables a program to deal with exceptional situations in an orderly manner

exception handling

using _____ you can define a general class and extend it into a more specialized class

inheritance

when an object reference can be typecast into another object reference it is called _____

casting

Converting a primitive value to a wrapper object is called _____.

boxing