Extra Exercises
Source:
Suggested but not selected midterm
questions
CSE 201 – Elementary Computer Programming
1
Checking if string has digit
 Given a string variable, inputName, check
to see if it contains any numbers. If it
contains any numbers, output an error
message.
 The boolean Character.isDigit(char) method
can be used to check a character variable to
see if it is a digit.
CSE 201 – Elementary Computer Programming
2
Reverse Guessing Game
 Write a program which plays the random number game,
 the user chooses the secret number between 1 and 10, the computer
will make "guesses" by choosing random numbers. User will enter ‘b’ is
secret number is bigger than guess, and ‘s’ if secret number is smaller
than guess, and ‘c’ when correct.
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Sample:
The code
9
int randomNumber = (int)(10 *
s
Math.random ()) + 1;
1
will generate a random number
b
between 1 and 10 and assign the
8
value to the variable
s
randomNumber.
3
c
Computer guessed the secret number in 4 guesses
CSE 201 – Elementary Computer Programming
3
Value of expressions
 Given the following variable declarations
int i = 10, j = 3, k = -1;
boolean b = true;
String str = "Elephant";
char c = 'e';
(A) evaluate expressions (a)-(f):
a. (i < j) || b
b. str.charAt(j)
c. str.length() == 7
d. str.substring(0,4)
e. str.indexOf(c)
f. str.indexOf('c')
CSE 201 – Elementary Computer Programming
4
Errors and Types
 Given the following variable declarations
int i = 10, j = 3, k = -1;
boolean b = true;
String str = "Elephant";
char c = 'e';
determine which of the following statements (g)-(j) will
produce an error. If a statement does produce an error,
what kind? Briefly explain in one or two sentences why it
produces an error.
a. (i < j) || b
b. str.charAt(j)
c. str.length() == 7
d. str.substring(0,4)
e. str.indexOf(c)
f. str.indexOf('c')
CSE 201 – Elementary Computer Programming
5
Code Writing
 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
6
Debug According to Description
//This program counts the number of special characters
//(&, @, and $) in a string input.
Scanner in = new Scanner(System.in);
String userInput;
System.out.print("Please enter a string: ");
userInput = in.nextLine();
int stringSize = userInput.length();
int counter = 0, numSpecialChars = 0; char letter;
while (counter < stringSize)
{
letter = userInput.charAt(counter);
if ((letter == '&') || (letter == '@') || (letter ==
'$'))
{
numSpecialChars = numSpecialChars + 1;
}
}
System.out.println("Number of special characters is " +
numSpecialChars );
CSE 201 – Elementary Computer Programming
7
If else
 Are the two set of statements equivalent.
Explain your answer in detail to get any
credit. You can assume x and y are
integers input by the user .
if( x = = y)
if( x = = y)
x = 5;
x = 5;
else
if( x != y)
x = 7;
x = 7;
CSE 201 – Elementary Computer Programming
8