Practice Test(s)

Question 1

Practice Test 01

What is the largest number of comparisons needed to perform a binary search on an array with 42 elements?

2

5

6

41

42

Answer 1

6

Question 2

Practice Test 01

Which of the following are valid arrays?

I. int[] coolArray = {1, 2, 3};

II. int[] threeThings = {1.0, 2.0, 3.0};

III. int[] = {“1”, “2”, “3”};

I only

II only

III only

I and II

I and III

Answer 2

I only

Question 3

Practice Test 01

What is the output of the following program?

1. hel
2. hello
3. hellow
4. Error
5. None of the above

Answer 3

4. Error

Correct! Specifically, the <= in the for loop results in an attempt to access data that is out of the array’s bounds.

Question 4

Practice Test 01

What values will the array contain after the following the code is run?

int[] someArray = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};

for (int i = someArray.length - 2; i >= 0; i-=2)

{

someArray[i] = someArray[i] - 5;

}

1. {6, 5, 4, 3, 2, 1, 0, -1, -2, -3, -4}
2. {1, -3, 3, -1, 5, 1, 7, 3, 9, 5, 11}
3. {1, 3, 5, 7, 9, 7, 5, 3, 1, -1, -3}
4. {-4, 1, -2, 3, -4, 5, -6, 7, -8, 9}

Answer 4

2. {1, -3, 3, -1, 5, 1, 7, 3, 9, 5, 11}

Question 5

Practice Test 01

What is the proper way to compare String values in Java?

1. The == operator
2. The .equals() String method
3. The = operator
4. The | operator

Answer 5

2. The .equals() String method

Question 6

Practice Test 01

What result would be printed given these commands:

SomeFavorites mystery = new SomeFavorites();

mystery. listSomething();
mystery. anotherThing();

Answer 6

42

42

Question 7

Practice Test 01

What are the values of the variables x, y, and z after this code snippet runs?

int x = 0;

int y = 10;

int z = 20;

x = y;

y = y * 2;

z = 30;

1. x = 0, y = 10, z = 30
2. x = 0 , y = 20 , z = 20
3. x = 10, y = 20, z = 30
4. x = 10, y = 10, z = 30

Answer 7

3. x = 10, y = 20, z = 30

Question 8

Practice Test 01

Your robot Baymax seems to have a bug in his battery. The problem is Baymax will only stay on if his battery is at 100%. Anything lower than 100% and Baymax shuts off. What is the bug in this code snippet?

Hint : Baymax represents his battery life as a decimal number between 0 and 1.

1. There is a syntax error in Baymax’s baymaxIsOn method. The else statement must also have a conditional expression.
2. We are trying to represent batteryLife (a decimal number) with an int variable. We should instead be using a double variable.
3. Baymax’s chargeBattery and useBattery methods will error. Java does not allow you to add an int and a double.
4. Baymax’s baymaxIsOn method can NEVER return True.

Answer 8

2. We are trying to represent batteryLife (a decimal number) with an int variable. We should instead be using a double variable.

Question 9

Practice Test 01

What would be a correct way to instantiate this 2D array?

1. int[][] table = {1, 0, 1, 5,
   3, 8};
2. int[][] table = { {1, 0, 1, 5},
   {3, 8} };
3. int[][] table = { {1, 0, 1, 5},
   {3, 8, 0, 0} };

Answer 9

2. int[][] table = { {1, 0, 1, 5},
   {3, 8} };

Question 10

Practice Test 01

Given the following:

double[][] something =
{ {2.5, 6.8, 8.3},
{6.1, 10.2, 1.3, -2.5},
{1.1, 2.3, 5.8, 13.21, 34.55} }

What is the value of something[1][2]?

6. 8
7. 1
8. 3
9. 3

The array does not have an element at that location.

Answer 10

1.3

Question 11

Practice Test 01

What is the proper way to get the number of items in an ArrayList called list?

1. list.length
2. list.size
3. list.length()
4. list.size()
   5.

Answer 11

4. list.size()

Question 12

Practice Test 01

What is the output of the following lines?

• int x = 24;*
• System.out.println(“The total is “ + x + x);*

1. The total is 24
2. The total is 2424
3. The total is 48
4. The total is x + x

Answer 12

2. The total is 2424

Question 13

Practice Test 01

Which expression is true?

1. true && !true
2. !false || !true
3. true && false
4. false || false || !true

Answer 13

2. !false || !true

Question 14

Practice Test 01

What will this program print if the value of grade is 80?

Answer 14

C

Question 15

Practice Test 01

What will the values of x and y be after this code segment runs?

Answer 15

x = 99

y = 199

Question 16

Practice Test 01

Refer to the following code segment:

double myDouble = 1/4;

System.out.println(“1 / 4 = “ + myDouble);

The output of the code is:

1 / 4 = 0.0

The student wanted the output to be:

1 / 4 = 0.25

Which change to the first line of their code segment would get the student the answer that they wanted?

1. int myDouble = 1/4;
2. double myDouble = (double) 1/4;
3. double myDouble = (int) 1/4;
4. double myDouble = (int) (1.0/4.0);

Answer 16

2. double myDouble = (double) 1/4;

Question 17

Practice Test 01

What will the following code print?

Answer 17

Java

Question 18

Practice Test 01

What is wrong with the following code?

ArrayList list = new ArrayList();

list.add(1);

System.out.println(list.get(0));

1. It will throw an IndexOutOfBoundsException.
2. You cannot use int as the type in an ArrayList.
3. list is a reserved word, so you can’t call the variable that.
4. You need to define the new ArrayList on a new line of code.
5. Nothing. The above code is correct.

Answer 18

2. You cannot use int as the type in an ArrayList

Question 19

Practice Test 01

What does this method call output?

public double doubleNumber(double myNumber)

{

return (double) (int) myNumber * 2;

}

doubleNumber(7.8);

16

15. 6
16. 0

This method is improperly written.

Answered

Answer 19

14.0

Question 20

Practice Test 01

Consider the following code segment:

String str = “I am”;
str += 10 + 3;
String age = “years old”;
System.out.println(str + age);

What is printed as a result of executing the code segment?

1. I am103years old
2. I am13years old
3. I am 103 years old
4. I am 13 years old

Answer 20

2. I am13years old

Question 21

Practice Test 01

What would this method call output?

divideByTen(340)

Answer 21

34

Question 22

Practice Test 01

What is the output of this method call?

public String wordScramble(String myWord)
{
myWord.substring(2) + myWord.charAt(3) + “dot”;
}

wordScramble(“polkadot”)

1. “dotpolka”
2. “lkadotkdot”
3. “olkadotldot”
4. This method call will error.

Answer 22

4. This method call will error

Question 23

Practice Test 01

What kind of error does this method cause?

myMethod(“Frog”);

1. Compile Time Error: Missing return value
2. Runtime Error: String index out of range
3. Compile Time Error: Unexpected return value
4. Compile Time Error: Syntax Error in method definition

Answer 23

2. Runtime Error: String index out of range

Question 24

Practice Test 01

What does this method call output?

someMethod(3,1)

Answer 24

10

Question 25

# Practice Test 01 **What is wrong with the class definition?** *Hint*: We expect names and types to be assigned as instance variables in the class constructor. 1. Missing void in constructor definition 2. Class constructors must be private 3. Arrays can not be passed as parameters to a constructor 4. Must use this in constructor when the constructor parameters have the same name as instance variables.

Answer 25

4. Must use this in constructor when the constructor parameters have the same name as instance variables.

Question 26

# Practice Test 01 What will the Array **gameBoard** contain after this code runs? 1. ["X", "O", "X", "O", "X", "O", "X", "O", "X"] 2. ["X", "O", "O", "X", "O", "O", "X", "O", "O"] 3. ["O", "X", "X", "O", "X", "X", "O", "X", "X"] 4. ["O", "X", "O", "X", "O", "X", "O", "X", "O"]

Answer 26

2. ["X", "O", "O", "X", "O", "O", "X", "O", "O"]

Question 27

# Practice Test 01 Finn just purchased the newest gaming system, the BMO 2600. Unfortunately, when Finn turned on the system, it froze on the loading screen! Help Finn identify the bug in the Java code running his new gaming system. **boolean onLoadingScreen = true;** **int loadingTime = 100;** **while(onLoadingScreen) {** **loadingTime++;** **onLoadingScreen = loadingTime != 0;** **}** 1. The != operator can not be used to compare ints. 2. The != operator does not return a boolean value. 3. The variable loadingTime is increasing instead of decreasing. 4. while statements loop infinitely. A for statement should be used instead.

Answer 27

3. The variable loadingTime is increasing instead of decreasing

Question 28

# Practice Test 01 Your friend is bored at lunch and is climbing the stairs for fun. He walks up two stairs, walks down one, walks up two stairs, walks down one, and so on. How many iterations of the while loop will it take her to walk up to the 10th stair?

Answer 28

9

Question 29

# Practice Test 01 All of your coins are inside a 3 x 4 matrix. Which piece of java code will properly find the total number of coins that you have? 1. int col = 0; col \< numCoins[row].length(); col++ 2. int col = 0; col \< numCoins.length + 1; col++ 3. int col = 0; col \< numCoins[row].length; col++ 4. int col = 0; col \< numCoins.length; col++

Answer 29

3. int col = 0; col \< numCoins[row].length; col++

Question 30

# Practice Test 01 What is the return value of this method call? ## Footnote **findTheMiddle(2110890125)**

Answer 30

89

Question 31

# Practice Test 01 Which methods of class Foo do not require an instance of class Foo to be invoked? 1. All methods require an instance of Foo to be invoked. 2. No methods require an instance of Foo to be invoked. 3. bar() 4. baz() 5. foo()

Answer 31

5. foo()

Question 32

# Practice Test 01 The Java Classes Skeleton, Spider, and Zombie all extend the Java Class Monster. The Monster Class is defined below. **What variables and methods do the Skeleton, Spider, and Zombie Classes inherit?** 1. Everything 2. Only the variables name and type 3. Only the variables 4. Only the methods 5. The variables name and type and the method move

Answer 32

5. The variables name and type and the method move

Question 33

# Practice Test 01 Given the definitions of class A and class B.... what is the output of this code **B obj = new B();** **System.out.println(obj.i + " " + obj.j);** 1. 1 2 2. 2 1 3. Runtime Error 4. Compilation Error

Answer 33

**1.** 1 2

Question 34

# Practice Test 01 Given the class definitions of Vector2D and Vector3D below, which of the constructors that follow would be valid in the Vector3D class? *Hint*: Which Vector3D class definitions will not cause an error? I, II, and III I and II II and III Only III Only II

Answer 34

I, II, and III

Question 35

# Practice Test 01 What is the correct pseudocode for Insertion Sort? 1. If there are at least two elements in the collection Partition the collection Insertion sort the left collection Insertion sort the right collection 2. If there is more than one element in the collection Break the collection into two halves Insertion sort the left half Insertion sort the right half Compare the two halves Merge the two subcollections into a sorted collection 3. Start with the first element and sort it with itself While there is a next element Compare the next unsorted element with the sorted elements Insert the element into the correct position in the sorted elements 4. While there are unsorted numbers Find the smallest unsorted number Insert the element at the end of the sorted elements

Answer 35

**3.** Start with the first element and sort it with itself While there is a next element Compare the next unsorted element with the sorted elements Insert the element into the correct position in the sorted elements

Question 36

# Practice Test 01 When the call mystery2() is executed, what are the values of word and num at the point indicated by */\* End of method \*/*?

Answer 36

``` word = peanut num = 7 ```

Question 37

What will be returned by **mystery**? 1. The minimum value in the array will be returned. 2. The maximum value in the array will be returned. 3. The length of the array will be returned. 4. No value will be returned. 5. All values in the array will be returned.

Answer 37

1. The minimum value in the array will be returned ## Footnote *Correct! Using the x = arr[0 [0] guarantees that the correct minimum value will be found and returned.*

Question 38

Given the following method declaration and int[] arr = {30, 7, 88, 17}, what is the value in arr[1] after the method is run? ## Footnote **public static int mystery(int[] arr)** **{** **arr[1]--;** **return (arr[1] \* 2);** **}**

Answer 38

6

Question 39

Refer to the following code snippet: **double result = 17 / 4;** **System.out.println("17 / 4 = " + result);** The output is **17 / 4 = 4.0** but the programmer intends the output to be **17 / 4 = 4.25** Which of the following replacements for the first line of code will **NOT** fix the problem? 1. double result = (double) (17 / 4); 2. double result = (double) 17 / 4; 3. double result = 17.0 / 4; 4. double result = 17 / (double) 4; 5. double result = (double) 17 / 4.0;

Answer 39

1. double result = (double) (17 / 4);

Question 40

Just before the end of execution of this program, what are the values of a, b, and temp, respectively? 1. 12, 17, 12 2. 17, 12, 12 3. 17, 12, 17 4. 17, 12, undefined 5. 12, 17, undefined

Answer 40

**5.** 12, 17, undefined ## Footnote *Primitive types are of the actual arguments when passed as parameters. So a and b are copied into the Mystery method as copies and the args remained unchanged. The local vartemp goes out of scope as soon as the Mystery method is done executing and is thus is undefined just before the end of the program execution.*

Question 41

Consider the following method modifyArray. An array is created that contains {1, 2, 4, 9, 5} and is passed to modifyArray. What are the contents of the array after the modifyArray method executes? 1. {1, 1, 2, 5, -4} 2. {11, -10, -8, -4, 5} 3. {3, 6, 13, 14, 5} 4. {21, 20, 18, 14, 5} 5. This method results in an IndexOutOfBounds exception.

Answer 41

4. {21, 20, 18, 14, 5} ## Footnote For every iteration of the loop, arr[i] and arr[i - 1] are added together and are assigned to arr[i - 1].

Question 42

What value is returned as the result of the call **mystery(6)**?

Answer 42

**48** The result from mystery(6) is 6 \* mystery(4) which is 4 \* mystery(2) which is 2\* mystery(0) which is 1, so the answer is 2 \* 4 \* 6 = 48.

Question 43

What is the output when the following code is compiled and run? **Flower flower = new Flower(3);** **Flower callaLily = new Lily(4);** **flower.showWater();** **flower.addWater();** **flower.showWater();** **callaLily.showWater();** **callaLily.addWater();** **callaLily.showWater();** 1. 3 4 3 4 2. 6 7 6 7 3. 3 4 8 9 4. The code won’t complile. 5. When callaLily.addWater() is executed a runtime error ClassCastException is thrown.

Answer 43

3. **3 4 8 9** An object always knows which class that created it, so even though callaLily is declared to be a Flower the constructor that is executed is the one for Lily.

Question 44

Which of the following is printed as a result of the call mystery(12345)? 1. 543210 2. 5432112345 3. 1551 4. 1234554321 5. Many digits are printed because this method creates an infinite recursion.

Answer 44

5. Many digits are printed because this method creates an infinite recursion ## Footnote *When the recursive call to mystery(1) occurs, x /10 evaluates to 0 because of integer division and the remainder is discarded. So the current 4th call to mystery will be completed as will all of the previous calls to mystery.*