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CSE142 Midterm
Autumn 2005
Name of Student_______________________________________________________________
Section (e.g., AA)___________________ TA_____________________________________
Exam time (9:30, 11:30)______________
This is an open-book/open-note exam. Space is provided for your answers. Use
the backs of pages if necessary. The exam is divided into seven questions with
the following points:
# Problem Area Points Score
---------------------------------------------
1 Expressions 10 _____
2 Parameter Mystery 20 _____
3 Simulation 15 _____
4 Assertions 15 _____
5 Programming 15 _____
6 Programming 15 _____
7 Programming 10 _____
----------------------------
Total 100 _____
The exam is not graded on style and you do not need to include comments. You
may use a calculator to do simple arithmetic, although you are not allowed to
program the calculator or to run a stored program.
Do not begin work on this exam until instructed to do so. Any student who
starts early or who continues to work after time is called will receive a 10
point penalty.
If you finish the exam early, please hand your exam to the instructor and exit
quietly through the front door.
1. Expressions, 10 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
3 * 4 + 5 * 6 __________
23 % 5 - 17 % (16 % 10) __________
"1" + 2 + 3 * 4 + (5 + 6) __________
1.5 * 2 + 20 / 3 / 4.0 + 6 / 4 __________
345 / 10 / 3 + 10 / (5 / 2.0) __________
2. Parameter Mystery, 20 points. Consider the following program.
public class Mystery {
public static void main(String[] args) {
String foo = "buzz";
String sam = "sue";
String sue = "foo";
String bill = "hope";
String hope = "bill";
say(sam, sue, foo);
say(foo, "bill", sam);
say(hope, bill, sue);
say(bill, hope, sam);
say("sue", "hope", hope);
}
public static void say(String foo, String sam, String sue) {
System.out.println(sam + " wants " + sue + " to " + foo + ".");
}
}
List below the output produced by this program.
3. Simulation, 15 points. Consider the following method:
public static int mystery(int z) {
int x = 1;
int y = 1;
while (z > 2) {
y = y + x;
x = y - x;
z--;
}
return y;
}
For each call below, indicate what value is returned.
Method Call Value Returned
mystery(1); _______________
mystery(3); _______________
mystery(4); _______________
mystery(5); _______________
mystery(6); _______________
4. Assertions, 15 points. You will identify various assertions as being either
always true, never true or sometimes true/sometimes false at various points
in program execution. The comments in the method below indicate the points
of interest.
public static int mystery(int x) {
int y = 1;
int z = 0;
// Point A
while (y <= x) {
// Point B
y = y * 10;
z++;
// Point C
}
// Point D
z--;
// Point E
return z;
}
Fill in the table below with the words ALWAYS, NEVER or SOMETIMES.
y > x z < 0 z > 0
+---------------------+---------------------+---------------------+
Point A | | | |
+---------------------+---------------------+---------------------+
Point B | | | |
+---------------------+---------------------+---------------------+
Point C | | | |
+---------------------+---------------------+---------------------+
Point D | | | |
+---------------------+---------------------+---------------------+
Point E | | | |
+---------------------+---------------------+---------------------+
5. Programming, 15 points. Write a method hasMidpoint that takes three
integers as parameters and that returns true if one of the numbers is the
midpoint of the other two and that returns false otherwise. A number is
considered the midpoint of two numbers if it appears halfway between them.
For example, 12 is the midpoint of 10 and 14. The numbers might be in any
order, so any one of the three might be the midpoint of the other two.
Write your solution to hasMidpoint below.
6. Programming, 15 points. Write a method printMultiples that takes an integer
n and an integer m as parameters and that prints a complete line of output
reporting the first m multiples of n. For example, the following calls:
printMultiples(3, 5);
printMultiples(7, 3);
should produce this output:
The first 5 multiples of 3 are 3, 6, 9, 12, 15
The first 3 multiples of 7 are 7, 14, 21
Notice that the multiples are separated by commas. You are to exactly
reproduce this format. Also notice the order of the parameters: the first
parameter is the base number and the second parameter is the number of
multiples to generate.
You may assume that the number of multiples you will be asked to generate is
greater than or equal to one. Write your solution to printMultiples below.
7. Programming, 10 points. Write a method printStripped that takes a String
as an argument and that prints a complete line of output with any comments
stripped from the String. Comments are defined to be characters enclosed in
the characters "<" and ">". More precisely, text is "normal" until you
encounter a "<" character. From that point on the text is considered a
comment until you encounter a ">" character, at which point you return to
normal text. This definition allows for "<" inside a comment and ">"
outside a comment. You may assume that there are no unclosed comments in
the String.
For example, the following sequence of calls:
printStripped("this is plain text");
printStripped("this has a normal comment <right here> to be removed");
printStripped("this has multiple less-than in a comment <<<<<see?>");
printStripped("this > has <comment>greater-than outside a comment >>");
printStripped("<hi>this has <foo> multiple <bar> comments<baz><>.");
should produce the following output:
this is plain text
this has a normal comment to be removed
this has multiple less-than in a comment
this > has greater-than outside a comment >>
this has multiple comments.
Write your solution to printStripped below.
]]>
Stuart Reges
Last modified: Fri Sep 16 15:34:53 PDT 2011