Extra Exercises
Sources
http://www.seas.upenn.edu/~cse110/exams/old/midterm1_fall05.pdf
http://www.csd.uwo.ca/courses/CS026b/oldmidt/midterm.doc
CSE 201 – Elementary Computer Programming
1
Value of The Variable x
 For each of the following program
fragments, what is the value of the
variable x after the statements execute?
(A)
int y = 5;
int x = y;
y = y * 2;
CSE 201 – Elementary Computer Programming
(B)
int x = 5;
x = x / 2;
x = x + 3 * x - 3;
2
Value of The Variable x
 For each of the following program
fragments, what is the value of the
variable x after the statements execute?
(C)
double x = 13 / 2;
(D)
boolean x = ( 2 == 3 );
CSE 201 – Elementary Computer Programming
3
Value of expressions
 What is the value of each of the following
valid expressions?
(a)
(2 < 2) || (2 > 2)
(b)
(!false) && (!false)
(c)
( 5 > 2 ) == ( 3 <= 3 )
CSE 201 – Elementary Computer Programming
4
Debug According to Description
 Fix the code so that it works according to
the supplied documentation (in comments)
/* Calculates sum of all of the even
* numbers from 0 to limit inclusive.
* Assumes limit is initialized above
* to a positive integer. */
int i = 0;
int sum = 0;
while (i != limit)
{
sum = sum + i;
i+=2;
}
CSE 201 – Elementary Computer Programming
5
Debug According to Description
 Solution
/* Calculates sum of all of the even
* numbers from 0 to limit inclusive.
* Assumes limit is initialized above
* to a positive integer. */
int i = 0;
int sum = 0;
while (i <= limit)
{
sum = sum + i;
i+=2;
}
CSE 201 – Elementary Computer Programming
6
How Many Iterations?
 How many times the body of the loop is executed?
 0, 1, infinite, or “> 1”?
 ”> 1” means more than once but not infinite.
int x=1;
while (x<10)
{
System.out.println(x);
}
CSE 201 – Elementary Computer Programming
7
How Many Iterations?
 How many times the body of the loop is executed?
 0, 1, infinite, or “> 1”?
 ”> 1” means more than once but not infinite.
int x=10;
while(x<10)
System.out.println(x);
x=x-1;
CSE 201 – Elementary Computer Programming
8
How Many Iterations?
 If we put a ; at while loop
 How many times x is printed?
int x=10;
while(x<10);
System.out.println(x);
x=x-1;
CSE 201 – Elementary Computer Programming
9
How Many Iterations?
 How many times the body of the loop is executed?
 0, 1, infinite, or “> 1”?
 ”> 1” means more than once but not infinite.
int x=1;
while(x!=10)
{
x = x*2;
}
CSE 201 – Elementary Computer Programming
10
True/False
 In Java I can have both mystring and myString
as two distinct variables in same program.
 When writing a computer program, everything
must be precise and unambiguous.
 The starting index position for a string in Java is
0.
 When a program written in Java is compiled, it is
typically compiled to bytecode
CSE 201 – Elementary Computer Programming
11
Multiple Choice 1
In Java, the calculation 3 % 4 produces a
result of:
a.
0
b.
1
c.
0.75
d.
3
e.
None of the above.
CSE 201 – Elementary Computer Programming
12
Multiple Choice
Which of the following represents a
character in Java:
a.
a
b.
'a'
c.
"a"
d.
All of the above.
e.
None of the above.
CSE 201 – Elementary Computer Programming
13
Multiple Choice
Which of the following is a valid way to create
a String object containing the text
“Hello there” in Java:
a.
String tempString = "Hello there";
b.
String tempString = "Hello" + " " +
"there";
c.
String tempString = new String("Hello
there");
d.
All of the above.
e.
None of the above.
CSE 201 – Elementary Computer Programming
14
Value and Type
 For each of the following Java expressions,
provide the result of evaluating the expression,
and identify the type of this value.
a.
"Java" +
"is" + "great"
b.
"123 + 456"
c.
3 / 2 * 1.0
d.
"The answer is: " + 5 + 5
e.
"The answer is: " + (5 + 5)
CSE 201 – Elementary Computer Programming
15
Value and Type
 For each of the following Java expressions,
provide the result of evaluating the expression,
and identify the type of this value.
f.
g.
'b' > 'a'
1 + 2 * 3 – 4 / 5
h.
(((int) 1.0) % 5 + 0.5 * 2) / 2.0 –
((double) 1)
i.
3 / 6 * (16.3 * 20.2 + 960 / 6.0)
CSE 201 – Elementary Computer Programming
16
Code Tracing
 Trace this code segment and report what this
code prints to the screen
int numPeople = 4;
System.out.println(numPeople);
double bill = 100.00;
System.out.println(bill);
double tip = bill * 0.2;
System.out.println(tip);
double total = bill + tip;
System.out.println(total);
double totalPerPerson = total / numPeople;
System.out.println(totalPerPerson);
CSE 201 – Elementary Computer Programming
17
Code Understanding
 What does this code do?
int sum = 0;
int i = 51;
while (i < 100) {
sum = sum + (i*i);
i++;
i++;
}
CSE 201 – Elementary Computer Programming
18
Code Understanding
 What does this code do?
int sum = 0;
int i = 51;
while (i < 100) {
sum = sum + (i*i);
i++;
i++;
}
CSE 201 – Elementary Computer Programming
19
Fix Code
 Fix code to implement a validation loop to
ensure that the user enters a number between 1
and 9 inclusive?
Scanner in = new Scanner(System.in);
int ans;
ans = in.nextInt();
while (ans > 0 && ans < 10)
{
ans = in.nextInt();
}
CSE 201 – Elementary Computer Programming
20
Code Understanding
 What does this code do?
String foo = "Java!";
String bar = "";
int i = 0;
while( i < foo.length())
{
bar = foo.charAt(i) + bar;
i++; //i.e i=i+1;
}
System.out.println(bar);
CSE 201 – Elementary Computer Programming
21