Itcs 2214 Data Structures Test 1 Review

Front 1

1. Write a for loop that displays the following set of numbers:
0, 10, 20, 30, 40, 50 . . . 1000.

Back 1

for(int i = 0; i <= 1000; i += 10)
System.out.print(i + “,”);

Front 2

2. Write a loop that asks the user to enter a number. The loop should iterate 10 times and keep a running total of the numbers entered.

Back 2

Scanner k = new Scanner(System.in);
int total = 0;
for(int i = 0; i < 10; i ++){
System.out.println(“Enter a number: “);
total += k.nextInt();
}

Front 3

3. Write a for loop that calculates the total of the following series of numbers:
1/30 + 2/29 + 3/28 + 4/27 + . . . 30/1

Back 3

double total = 0;
for(int i = 1; i < 31; i ++){
total += (i / (31 – i));
}

Front 4

4. Write a nested loop that displays 10 rows of ‘#’ characters. There should be 15 ‘#’ characters in each row.

Back 4

for(int i = 0; i < 10; i ++){
for(int j = 0; j < 15; j++){
System.out.print(“#”);
}
System.out.println();
}

Front 5

5. Covert the while loop in the following code segment to a for loop:
int count = 0;
while (count < 50)
{
System.out.println(“count is “ + count);
count++;
}

Back 5

for(int i = 0; i < 50; i++)
System.out.println(“count is “ + i);

Front 6

In regards to fields and methods, what happens when one class inherits from another?

Back 6

You're allowed to use all the methods

Front 7

Explain what a reference alias is:

Back 7

2 reference variables that refer to the same object

Front 8

Explain what a static field is (a field is a variable):

Back 8

Static fields are created in memory one time. Variable that is shared among off classes. All objects share the same value when you have a static field

Front 9

Explain what a static modifier on method headers means

Back 9

Allows you to call the method without creating an object. You do not have to call the method through the object.

Front 10

Explain the null keyword and why it’s used:
if(object != null)

Back 10

Reference variable does not hold value or doesn’t point to an object. Used to see if it in fact does point to the object.

Front 11

polymorphism:

Back 11

Reference variable can point to an object of its declared type or any object that extends from that object

Front 12

super() reference:

Back 12

the one the class extends from. Refers from the class directly above

Front 13

Describe "is-a" relationship

Back 13

a relationship that only goes one way.
ex: a thumb is a finger but a finger is not a thumb.

Front 14

Inheritance is the process of deriving:

Back 14

a new class from an existing one.
also to reuse existing software

Front 15

wrapper classes do:

Back 15

they "wrap" the primitive data type into an object of that class.

ex: Integer n = new Integer (15);

Front 16

explain how does a try/catch works:

Back 16

Each catch clause on a try statement
handles a particular kind of exception
that may be thrown within
the try block.

Front 17

Why would you use try/catch blocks:

Back 17

to guard against and handle a run-time error

Front 18

What is an advantage of an ArrayList:

Back 18

ArrayList don’t have a set limit or size

Front 19

What is an disadvantage of an ArrayList:

Back 19

ArrayList only hold objects

Front 20

Write the code to loop through and output all the elements of a given ArrayList:

Back 20

for(int i =0; i < staff.size(); i++)

REMEMBER ARRAYLIST USES .SIZE
ARRAY USES .LENGTH

Front 21

ArrayList<Player> band = new ArrayList<Player>();
Player p1 = new Player(“Joe”, 12, “Center”);

Write the code to add the Player object (p1) to the ArrayList.

Back 21

band.add(p1);

Front 22

Given that there is an ArrayList named list that contains 5 Player objects, write the code to call and output the getPoints() method of the third element in list. The getPoints() method accepts no parameters and returns an int value.

Back 22

System.out.println(list.get(2).getPoints());

Front 23

Given that there is an ArrayList named staff that contains Employee Objects, write the code that will loop through staff, calling and outputting the toString() method for each Employee object.

Back 23

for(int i =0; i < staff.size(); i++){
System.out.println(staff.get(i).toString());
}

Front 24

ArrayList list = new ArrayList();
int num = 14;

Write the code to add the value contained in num to the ArrayList. Remember that ArrayLists can only hold objects.

Back 24

list.add(new Integer(num));

Front 25

Complete method getTotalPoints, which returns the total points of a given set of objects.

//precondition: list is a non-empty ArrayList containing Player objects.
//postcondition: returns the total of the int values stored in the points
field of the Player objects contained inside the ArrayList.
//the Player class contains method getPoints() which returns the point field
of the Player object.

Back 25

public static double getTotalPoints (ArrayList list){
double total = 0.0;
for(int i = 0; i < list.size(); i++){
total += list.get(i).getPoints();
}
Return total;
}

Front 26

Create a program (driver) that generates fifty random numbers in the 1 – 100 (inclusive) range. Your program should store those numbers into an array. The program should then create a chart showing how often a range of numbers is represented (see chart below). For example, if three of the fifty random numbers are between 11 and 20, there should be three * marks in the 11-20 row.

Back 26

import java.util.Random;

public class Rainfall {
public static void main(String[] cheese){

Random rand = new Random();
int[] numbers = new int[50];
String[] output = {"", "", "", "", "", "", "", "", "", ""};

for(int i = 0; i < numbers.length; i++){
numbers[i] = rand.nextInt(100) + 1;
}

for(int i = 0; i < numbers.length; i++){
int index = (numbers[i] - 1) / 10;
output[index] += "*";
}

for(int i = 0; i < output.length; i++){
System.out.println((i*10 + 1) + "-" + (i*10 + 10) + ": " + output[i]);
}
}
}

Front 27

The Boolean Expression: !(A || B) is equivalent to which of the following?

a. A != B
b. !A || B
c. A && B
d. !A || !B
e. !A && !B

Back 27

E. !A && !B

Front 28

The Boolean Expression: !((A < B) && (C > D)) is equivalent to which of the following?

a. (A < B) || (C > D)
b. (A >= B) && (C <= D)
c. (A >= B) || (C <= D)
d. (A > B) && (C < D)
e. (A > B) || (C < D)

Back 28

C. (A >= B) || (C <= D)

Front 29

Write the code that creates an object of the Scanner class. Use that object to take a String variable name, and set it equal to what the user types into the keyboard.

Back 29

Scanner k = new Scanner(System.in);

Front 30

Based on the following code, what data type does the determineHeight method return?

double armLength = 18.3;
double legLength = 20.5;
int bodyLength = 13;
int age = 15;
double height = determineHeight(armLength, legLength, bodyLength, age);

Back 30

double armLength = 18.3;
double legLength = 20.5;
int bodyLength = 13;
int age = 15;

Front 31

Queues
Where are new elements added

From where are elements removed

Back 31

Back

Front

Front 32

Given an implementation, determine the order in which elements are removed in a queue:

Back 32

First In First Out - FIFO

Front 33

Stacks
Where are new elements added

From where are elements removed
top or front

Back 33

top or front

top or front

Last In First Out-LIFO

Front 34

what does this do:

.hasNext()

Back 34

gives us next value

Front 35

what does this do:

.add(e)

Back 35

add and element to stack or queue

Front 36

what does this do:

peek()

Back 36

looks at top element w/o removing it from stack

Front 37

what does this do:

pop()

Back 37

used to remove the object at the top of this stack and returns that object as the value of this function.

Front 38

what does this do:\

push()

Back 38

This method pushes an item onto the top of this stack