Transcript CSCI 312 – Data Communication and Computer Networks

CSCI 160
Midterm Review
Rasanjalee DM
Multiple Choice Questions
Question
• The Java compiler translates Java programs
into machine language programs.
TRUE FALSE
Answer
• The Java compiler translates Java programs
into machine language programs.
• [FALSE]
Question
• System.out is an example of a method.
TRUE FALSE
Answer
• System.out is an example of a method.
TRUE FALSE
[FALSE]
Question
• ice-cream is an illegal identifier in Java.
• TRUE FALSE
Answer
• ice-cream is an illegal identifier in Java.
• TRUE FALSE
• [TRUE]
Question
• Constructors have return type void.
• TRUE FALSE
Answer
• Constructors have return type void.
• TRUE FALSE
• [FALSE]
Fill in the Blanks
Questions
• Every variable in Java must be __________
before it is used.
• Single quotes are used with constants of the
__________ type.
Answers
• Every variable in Java must be __________
before it is used.
[declared]
• 2. Single quotes are used with constants of the
__________ type.
[char]
Questions
• A(n) __________ is used for signaling the end
of the input.
• A(n) __________ is an action that an object
can take and is specified in the class definition.
• Compiling a file called Game.java will produce
a file called __________.
Answers
• A(n) __________ is used for signaling the end of the
input.
[sentinel value]
• A(n) __________ is an action that an object can take
and is specified in the class definition.
[method]
• Compiling a file called Game.java will produce a file
called __________.
[Game.class]
Question
• A(n) __________ is a data item that belongs to an
object.
• __________ is the word used to say that there
are no restrictions on the use of a method or data
item can be used.
• The reserved word __________ can be used as a
name for the calling the current object.
Answer
• A(n) __________ is a data item that belongs to an object.
• [instance variable]
• 4. __________ is the word used to say that there are no
restrictions on the use of a method or data item can be
used.
• [public]
• 5. The reserved word __________ can be used as a name
for the calling object.
• [this]
Short Answer Questions
Question
• Add parentheses to the following expressions
to indicate how Java will interpret them.
(a) a * b * c - d / e
(b) a + - b * c - d
Answer
(a)
(b)
((a * b) * c) - (d / e)
(a + ((-b) * c)) - d
Question
• After the following statements have been
executed, how many Fraction objects will
exist, not counting garbage objects?
Fraction f1 = new Fraction(1, 2);
Fraction f2 = new Fraction(3, 5);
Fraction f3 = f2;f2 = null;f1 = f2;
Answer
• One
Question
• Answer the questions
below about this class.
a)
b)
c)
d)
e)
What are the names of the
instance variables declared in
this class?
What are the signatures of the
constructors declared in this
class?
What are the names of the
parameters declared in this
class?
What are the signatures of the
methods declared in this class?
What are the names of the
constants declared in this
class?
Answer
• Answer the questions below about this class.
a) What are the names of the instance
variables declared in this class?
name, slalomPoints, giantSlalomPoints,
superGPoints, ussaNumber
b) What are the signatures of the constructors
declared in this class?
public Skier (String name, String
ussaNumber)
c)
What are the names of the parameters
declared in this class?
name, ussaNumber
d) What are the signatures of the methods
declared in this class?
public String getBestEvent()
e) What are the names of the constants
declared in this class?
MAXIMUM_POINTS
Code Analysis
Question
• What does the following program print?
int[] arr = {1, 1, 0, 0, 0};
for (int i = 2; i < arr.length; i++)
arr[i] = arr[i-1] + arr[i-2];
Answer
• What does the following program print? 11235
index =
0 1
2
3
4
int[] arr = {1, 1, 0, 0, 0};
for (int i = 2; i < arr.length; i++)
arr[i] = arr[i-1] + arr[i-2];
i
2
3
4
arr[i-1]
1
2
3
arr[i-2]
1
1
2
arr[i]
1+1 =2
2+1 =3
2+3 = 5
arr
11200
11230
11235
Question
• Show the EXACT output the following programs
generate:
public class e21 {
public static void main (String args[]) {
int num = 4;
printNumbers(num);
}
private static void printNumbers(int n) {
for (int i=1; i <= n; i++) {
for (int k=1; k <= 2*(i-1)+1; k++)
System.out.print(i);
System.out.println();
}
}
}
Answer
1
222
33333
4444444
Write Java Code
Question
• Write one line java statement declaring and
creating a 1-d double array that stores
whether or not precipitation was recorded on
each day of one (non-leap year)
Answer
• boolean[] precipRecord = new boolean[365];
Question
• Write a one-line java statement declaring and
creating a 2-d array named matrix with 24
rows and 80 columns.
Answer
• double[][] matrix = new double[24][80];
Question
• Write 1 or more java statements to display all
the elements of the last column of the 2-d
array matrix from the previous part
Answer
for(int i=0; i<matrix.length; i++)
System.out.println(matrix[i][79]);
Question
• Write 1 or more java statements to compute
and print the product of all the elements in
the second row of the 2-d array matrix
Answer
double product = 1
for(int i=0; i<matrix.length; i++)
{
product *= matrix[1][i];
}
System.out.println(product);
Question
• Write 1 or more java statements to compute
and print the number of upper case characters
in a saying (stored in variable saying)
Answer
int upper= 0;
for(int i=0;i<saying.length;i++)
{
if(saying.charAt(i)>=‘A’ && saying.charAt(i)<=‘Z’)
{
upper+;
}
}
System.out.println(upper);
Question
• Write a method named toBinary that accepts
an integer as a parameter and returns a string
of that number's representation in binary. For
example, the call of toBinary(42) should return
"101010". We will assume a positive
parameter.
Answer
private static String toBinary(int num)
{
if (num == 0)
return "0";
String str="";
while (num != 0)
{
str = (num%2)+str;
num /= 2;
}
return str;
}