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CSE142 Sample Final handout #26
1. Expressions, 5 points. For each expression in the left-hand column,
indicate its value in the right-hand column. Be sure to list a constant of
appropriate type (e.g., 7.0 rather than 7 for a double, Strings in quotes).
Expression Value
(6 + 7)/4/2.0 __________
13/2 * 3 % 10 - 1 __________
30/(2 * 6) + 1.5 __________
13 % 5 + 5 * 3/4 __________
"3 * 4" + 3 * 4 + 10 __________
2. 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 = 2; i < list.length; i++) {
list[i] = list[i] + list[i - 1] + list[i - 2];
}
}
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
------------------------------------------------------------
(8) ____________________________
() ____________________________
(3, 0, 1, 4, 7) ____________________________
(0, 1, 2, 3, 4, 5) ____________________________
(7, 4, -10, 8, 2) ____________________________
3. Polymorphism, 6 points. Assume the following classes have been defined:
public class Mammal extends SeaCreature {
public void method1() {
System.out.println("warm-blooded");
}
}
public class SeaCreature {
public void method1() {
System.out.println("creature 1");
}
public void method2() {
System.out.println("creature 2");
}
public String toString() {
return "ocean-dwelling";
}
}
public class Whale extends Mammal {
public void method1() {
System.out.println("spout");
}
public String toString() {
return "BIG!";
}
}
public class Squid extends SeaCreature {
public void method2() {
System.out.println("tentacles");
}
public String toString() {
return "squid";
}
}
Consider the following code fragment:
SeaCreature[] elements = {new Squid(), new Whale(), new SeaCreature(),
new Mammal()};
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?
4. Token-Based File Processing, 9 points. Write a static method processData
that takes as a parameter a Scanner holding a sequence of integers and that
reports each of the cumulative sums of the sequence along with the average
of the numbers. For example, if the Scanner contains the following data:
8 4 2 9 7 13 5 9
your method should produce the following output:
Sum of 1 = 8
Sum of 2 = 12
Sum of 3 = 14
Sum of 4 = 23
Sum of 5 = 30
Sum of 6 = 43
Sum of 7 = 48
Sum of 8 = 57
Average = 7.125
Notice that the various lines of output report the sum including just the
first number, then including the first two numbers, then including the first
three numbers, and so on, up to the sum including all numbers. The final
line of output reports the average of the sequence of numbers. Notice that
this is the average of the numbers themselves, not the average of the
cumulative sums.
The amount of output will vary depending upon how many numbers are in the
sequence. For example, if the Scanner contains the following values:
1 2 3 4
the method should produce the following output:
Sum of 1 = 1
Sum of 2 = 3
Sum of 3 = 6
Sum of 4 = 10
Average = 2.5
You are to exactly reproduce the format of these sample outputs. You may
assume that the Scanner has at least one integer to be processed.
Write your solution to processData below.
5. Line-Based File Processing, 10 points. Write a static method processFile
that takes a Scanner containing an input file as a parameter and that prints
the output file with certain lines underlined. The lines to be underlined
will all begin with a period. The period should not be printed. You should
print the text that follows the period on a line by itself followed by a
line of dashes that is equal in length to the text that follows the period.
For example, given the following input file:
.Statement of Purpose
I didn't expect to major in computer science until I took cse142.
I liked it more than I expected and that got me hooked on cs.
.High School Performance
I got very good grades in high school, graduating in the top 10% of
my class.
.College Performance
I have done well in my college classes, with an overall gpa of 3.5.
Your method should print the following output:
Statement of Purpose
--------------------
I didn't expect to major in computer science until I took cse142.
I liked it more than I expected and that got me hooked on cs.
High School Performance
-----------------------
I got very good grades in high school, graduating in the top 10% of
my class.
College Performance
-------------------
I have done well in my college classes, with an overall gpa of 3.5.
Notice that some of the input lines can be blank lines.
Write your solution to processFile below.
6. Arrays, 10 points. Write a static method printNumber that takes an array of
integers that represent the digits of a large integer and that prints the
integer with commas between every 3 digits starting from the right. Each
array element will store one digit of the number with array element 0
storing the first digit of the number, array element 1 storing the second
digit of the number and so on. You may assume that the values in the array
are all between 0 and 9 and that there are no leading 0's. For example, if
the array contains the digits (1, 5, 0, 0), then your method should produce
the following output:
1,500
If the array instead contains the digits (3, 8, 4, 9, 2, 1, 4, 7), then your
method should produce the following output:
38,492,147
Your method might not print any commas if the number is small enough. For
example, if the array contains the digits (2, 5, 0), then your method should
produce the following output:
250
Your method should produce an entire line of output so that if it is called
several times in a row, each call will produce a separate line of output.
7. ArrayList, 10 points. Write a static method manyStrings that takes an
ArrayList of Strings and an integer n as parameters and that replaces every
String in the original list with n of that String. For example,
suppose that an ArrayList called "list" contains the following values:
("squid", "octopus")
And you make the following call:
manyStrings(list, 2);
Then list should store the following values after the call:
("squid", "squid", "octopus", "octopus")
As another example, suppose that list contains the following:
("a", "a", "b", "c")
and you make the following call:
manyStrings(list, 3);
Then list should store the following values after the call:
("a", "a", "a", "a", "a", "a", "b", "b", "b", "c", "c", "c")
You may assume that the ArrayList you are passed contains only Strings and
that the integer n is greater than 0.
Recall that the primary methods for manipulating an ArrayList are:
add(Object value) appends value at end of list
add(int index, Object value) inserts given value at given index,
shifting subsequent values right
clear() removes all elements of the list
get(int index) returns the value at given index
remove(int index) removes value at given index, shifting
subsequent values left
set(int index, Object value) replaces value at given index with
given value
size() returns the number of elements in list
Write your solution to manyStrings below.
8. Critters, 15 points. Write a class Ant that implements the Critter
interface. The instances of the Ant class go through cycles of ten moves.
For each cycle, the Ant randomly chooses between going north-east or going
south-west (each choice should be equally likely). For a north-east cycle,
the ant goes north 5 times and then goes east 5 times. For a south-west
cycle, the ant goes south 5 times and then goes west 5 times. Each Ant
object should return the letter "A" for display purposes.
Remember that the Critter interface is defined as follows:
public interface Critter {
public char getChar();
public int getMove();
<definitions for constants NORTH, SOUTH, EAST and WEST>
}
Write your solution to the Ant class below.
9. Arrays, 15 points. Write a static method interleave that takes two arrays
of integers as parameters and that returns a new array that contains the
result of interleaving the elements of the two arrays. It should not alter
either of its parameters. Two arrays are interleaved by taking elements in
the following order:
1st element of 1st list
1st element of 2nd list
2nd element of 1st list
2nd element of 2nd list
3rd element of 1st list
3rd element of 2nd list
and so on
For example, if the variables list1 and list2 contain the following values:
list1: (1, 8, 3, 9)
list2: (2, 12, 6, 14)
Then the call interleave(list1, list2) should return a new array that stores
the following values:
(1, 2, 8, 12, 3, 6, 9, 14)
The order of the parameters matters. For example, interleave(list2, list1)
should produce the following array as its result:
(2, 1, 12, 8, 6, 3, 14, 9)
One list might be longer than the other, in which case any extra values from
the longer list should simply be appended at the end of the result. For
example, given the following lists:
list1: (1, 8, 3, 9)
list2: (82, 7, 4, 2, 1, 6, 5, 0, 18)
The call interleave(list1, list2) should produce the following result:
(1, 82, 8, 7, 3, 4, 9, 2, 1, 6, 5, 0, 18)
Notice that the first four values of the two arrays have been interleaved
and the excess values from the second list (1, 6, 5, 0, 18) have been
included at the end of the result. In this case the second list was longer,
but it could be the case that the first list is longer. Either list could
also be empty, in which case the result should contain the values from the
other list. Notice that your method is to return a new array.
Write your solution to interleave below.
10. Programming, 10 points. Write a static method indexOf that takes two
arrays of integers and that returns the index of the first occurrence of
the first list in the second list or -1 if the first list does not appear
in the second list. For example, suppose that you have two integer arrays
called list1 and list2 that store the following values:
list1: (1, 3, 5, 8, 12, 1, 3, 17, 1, 3, 6, 9, 1, 3, 6)
list2: (1, 3, 6)
then the call:
indexOf(list2, list1)
should return 8 because the sequence of values stored in list2 appears in
list1 starting with index 8. Notice that list2 actually appears twice in
list1, starting at position 8 and starting at position 12. Your method is
to return the first such position.
If the second list is not contained in the first list, then the method
should return the value -1. For example, if list1 had the same value as
before but list2 stored (12, 1, 3, 6), then the call indexOf(list2, list1)
should return -1 because list2 is not contained in list1. If the first
list is empty, your method should return 0.
Write your solution to indexOf below.
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