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CSE142 Sample Final, Spring 2022 handout #18
1. Reference Mystery, 5 points. What output is produced by this program?
import java.util.*;
public class ReferenceMystery {
public static void main(String[] args) {
int x = 1;
int y = 7;
int[] data = {2, 4, 6};
mystery1(data[x], data);
System.out.println(x + " " + Arrays.toString(data));
x = mystery2(x, y);
System.out.println(x + " " + y);
}
public static void mystery1(int z, int[] numbers) {
z = z + 3;
numbers[z / 3]++;
z = 3;
numbers[z - 2]--;
System.out.println(z + " " + Arrays.toString(numbers));
}
public static int mystery2(int x, int y) {
y++;
x = x + y;
return x + y;
}
}
2. Array Simulation, 10 points. You are to simulate the execution of a method
that manipulates an array of integers. Consider the following method:
public static void mystery(int[] list) {
for (int i = 1; i < list.length - 1; i++) {
if (i % 2 == 0) {
list[i] = list[i] - list[i - 1];
} else {
list[i] = list[i] + list[i - 1];
}
}
}
In the left-hand column below are specific lists of integers. You are to
indicate in the right-hand column what values would be stored in the list
after method mystery executes if the integer list in the left-hand column
is passed as a parameter to mystery.
Original List Final List
------------------------------------------------------------
{1} ____________________________
{2, 5, 9} ____________________________
{2, 3, 7, 2} ____________________________
{2, 4, 5, 4, 3} ____________________________
{5, 1, 8, 4, 8, 4} ____________________________
3. Inheritance, 6 points. Assume the following classes have been defined:
public class A extends D {
public String toString() {
return "a";
}
public void method1() {
System.out.println("a 1");
}
}
public class B extends C {
public String toString() {
return "b";
}
}
public class C extends D {
public void method1() {
System.out.println("c 1");
}
}
public class D {
public String toString() {
return "d";
}
public void method1() {
System.out.println("d 1");
}
public void method2() {
System.out.println("d 2");
}
}
Consider the following code fragment:
D[] elements = {new C(), new A(), new D(), new B()};
for (int i = 0; i < elements.length; i++) {
System.out.println(elements[i]);
elements[i].method1();
elements[i].method2();
System.out.println();
}
What output is produced by this code? Write the output as a series of
3-line columns in order from left to right (do not label columns or rows).
4. Token-Based File Processing, 10 points. Write a static method called
switchData that takes as a parameter a Scanner containing a label followed
by a sequence of integers and that prints to System.out the same information
with each successive pair of integers switched in order. For example,
suppose that a Scanner called data contains the following tokens:
Jan 1 2 3 4 5 6
Here the label is "Jan". The label will always be a single word that
appears at the beginning. After the label, we have a series of six
integers. If we make the following call:
switchData(data);
the method should produce the following output:
Jan 2 1 4 3 6 5
Notice that the first pair of integers (1, 2) has been switched (2, 1), and
the second pair of integers (3, 4) has been switched (4, 3), and so on.
This first example involved sequential integers to make the switching more
obvious, but this won't always be the case. You also shouldn't assume that
you have an even number of integers. If there is an odd number of integers,
then the final value should not be moved. For example, if the Scanner had
instead contained these tokens:
Feb 38 14 79 4 -3
then the method would have produced the following output:
Feb 14 38 4 79 -3
There will always be a one-word label, but the list of integers might be
empty, in which case the method simply prints the label on a line by itself.
Your method should produce a complete line of output. In other words, if it
is called n times, it will produce n lines of output. You may assume that
the input is legal (a one-word label followed by 0 or more integer values).
You may not construct any extra data structures to solve this problem.
5. Line-Based File Processing, 9 points. Write a static method called
analyzeParagraphs that takes as a parameter a Scanner containing a text file
and that produces output that describes the paragraph structure of the file,
returning the maximum number of lines in any given paragraph. Each
paragraph in the input file will be terminated by the text "<p>" on a line
by itself. For example, consider the following input file:
This is an example of an input file
with four different paragraphs.
<p>
The second paragraph is the longest
with three lines, so your method should
return 3 when processing this file.
<p>
<p>
The third paragraph was empty. This one is just short.
<p>
The method should count the number of lines in each paragraph and report
that information to System.out. For example, if the input above is stored
in a Scanner called input and we make the following call:
int max = analyzeParagraphs(input);
It should produce the following output:
2-line paragraph
3-line paragraph
0-line paragraph
1-line paragraph
It would assign max the value 3 because the method returns the maximum
number of lines in any given paragraph. You must exactly reproduce the
format of this output. You may assume that the input file has no blank
lines, that it contains at least one paragraph, and that each paragraph is
terminated by a line containing just "<p>". You may not construct any extra
data structures to solve this problem.
6. Arrays, 10 points. Write a static method called isAllPairs that takes an
array of integers as a parameter and that returns whether or not the array
is made up entirely of pairs of the same value. For example, if a variable
called "list" stores the following values:
{3, 3, 4, 4, 5, 5, 6, 6, 7, 7}
| | | | | | | | | |
+--+ +--+ +--+ +--+ +--+
pair pair pair pair pair
then the following call:
isAllPairs(list)
should return true because the array is entirely made up of pairs of the
same value: the first two values are both 3, the second two values are both
4 and so on.
Your method should return false if passed an array with an odd number of
values. You may assume that the array contains at least one value.
Below are several sample calls.
Contents of Array Value Returned
------------------------------------------------------------
{1} false
{1, 1} true
{1, 1, 2, 2, 3, 3} true
{2, 2, 55, 55, 33, 33, 33, 33}; true
{2, 2, 5, 5, 6, 7, 3, 4} false
{3, 3, 2, 4, 4}; false
{2, 2, 1, 1, 1}; false
7. ArrayList, 10 points. Write a static method called split that takes an
ArrayList of integer values as a parameter and that replaces each value in
the list with a pair of values, each half the original. If a number in the
original list is odd, then the first number in the new pair should be one
higher than the second so that the sum equals the original number. For
example, if a variable called list stores this sequence of values:
[18, 7, 4, 24, 11]
The number 18 is split into the pair (9, 9), the number 7 is split into (4,
3), the number 4 is split into (2, 2), the number 24 is split into (12, 12)
and the number 11 is split into (6, 5). Thus, the call:
split(list);
should cause list to store the following sequence of values afterwards:
[9, 9, 4, 3, 2, 2, 12, 12, 6, 5]
You may assume that all numbers in the list are nonnegative. You may not
construct any extra data structures to solve this problem. You must solve
it by manipulating the ArrayList you are passed as a parameter. See the
cheat sheet for a list of available ArrayList methods.
8. Critters, 15 points. Write a class called Sponge that extends the Critter
class. The instances of the Sponge class infect if an enemy is front of
them, hop if there is an empty space in front of them, and otherwise turn
left or right. They display themselves as square brackets with one or more
dashes inside, as in "[-]" or "[----]". They are always colored yellow.
They should always display at least one dash and should initially display
one dash. Each time a Sponge infects, it increases the number of dashes in
the display by one and each time a Sponge turns it decreases the number of
dashes in the display by one unless it has gotten down to a single dash. In
deciding which direction to turn, each Sponge should follow a pattern that
repeats every three turns. The first turn should be left and the second and
third turns should be right. Then it repeats with another left turn
followed by two right turns, and so on.
As in assignment 8, fields must be declared private, fields initialized to a
non-default value must be set in a constructor, and all updates to fields
must occur in the getMove method.
9. Arrays, 15 points. Write a static method called surroundWithN that takes
two arrays of integers and an integer n as parameters and that returns a new
array that contains the result of adding the first n values from the second
array at both the front and the back of the first array. For example if the
variables list1 and list2 contain the following values:
list1: [2, 8, 17, 3, 9, 0] list2: [103, 72, -8, 15, 42]
The call surroundWithN(list1, list2, 3) should return a new array storing:
[103, 72, -8, 2, 8, 17, 3, 9, 0, 103, 72, -8]
| | | | | |
+--------+ +---------------+ +--------+
from list2 list1 from list2
Notice that the new array has the first three values from list2 followed by
the values from list1 followed by the first three values from list2.
You may assume that the value n passed as a parameter is legal (between 0
and the length of the second array).
Your method should not construct any extra data structures other than the
array to be returned and it should not alter its two array parameters. You
are not allowed to call methods of the Arrays class to solve this problem.
10. Programming, 10 points. Write a static method called acronym that takes as
a parameter a string containing a phrase and that returns a string that has
the acronym for the phrase. For example, the following call:
acronym("self-contained underwater breathing apparatus")
should return "SCUBA". The acronym is formed by combining the capitalized
first letters of each word in the phrase. Words in the phrase will be
separated by some combination of dashes and spaces. There might be extra
spaces or dashes at the beginning or end of the phrase. The string passed
as a parameter will not contain any characters other than dashes, spaces,
and letters, and is guaranteed to contain at least one word. Below are
several sample calls.
Method Call Value Returned
----------------------------------------------- --------------
acronym(" automatic teller machine ") "ATM"
acronym("personal identification number") "PIN"
acronym("computer science") "CS"
acronym("merry-go-round") "MGR"
acronym("All my Children") "AMC"
acronym("Troubled Assets Relief Program") "TARP"
acronym("--quite-- confusing - punctuation-") "QCP"
acronym(" loner ") "L"
You are allowed to construct extra data structures to solve this problem
(an array, ArrayList, Scanner, String, etc), but you may use only methods
listed on the cheat sheet.
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