Transcript Lab04

ITI 1120
Lab #4
Branching
Contributors: G. Arbez, M. Eid, D.
Inkpen, A. Williams, D. Amyot
Exercise 1
Terminal/Output Screen
Program Memory
/* Lab 2, Exercise 1. */
class Tracing // Replace 'Template' with your own algorithm name.
{
// the main method contains all interactions with the user
public static void main (String[] args)
{
// prompt the user to enter 3 numbers
System.out.print( "Enter three floating-point values separated
by spaces: " );
// receive the numbers from keyboard and save in 3 variables
double number1 = input.nextDouble(); // read first double
double number2 = input.nextDouble(); // read second double
double number3 = input.nextDouble(); // read third double
Enter three floating-point values separated by spaces:
23.6 12.9 105.2
Maximum is: 105.2
Working Memory
number1
Number2
// determine the maximum value
double result = maximum( number1, number2, number3 );
Number3
// display maximum value
System.out.println( "Maximum is: " + result );
Result
}
public static void maximum(double x, double y,double z)
{
double maximumValue = x; // assume x is the largest to start
// determine whether y is greater than maximumValue
if ( y > maximumValue )
maximumValue = y;
// determine whether z is greater than maximumValue
if ( z > maximumValue )
maximumValue = z;
return maximumValue;
}
} // Don't remove this brace bracket!
x
y
z
maximumValue
Boolean Expressions
• Evaluate to true or false
• Translations from pseudocode to Java for:
Pseudocode

AND
OR
NOT
A=B
A≤B
AB
AB
Java
= (not a Boolean expression)
&&
||
!
A == B
A <= B
A >= B
A != B
Boolean Expressions, Example 1
• Write a test that returns TRUE if integer
I is odd; the test should return FALSE
otherwise.
Algorithm:
Java:
I mod 2 = 0 ?
false
odd 
TRUE
true
odd 
FALSE
// assume i has a value
boolean odd;
if (i % 2 == 0)
{
odd = false;
}
else
{
odd = true;
}
Boolean Expressions:
• Write a test that returns TRUE if integer
I is a multiple of positive integer K; the
test should return FALSE otherwise.
Algorithm:
Java:
I mod K = 0 ?
false
multiple 
FALSE
true
multiple 
TRUE
// assume i, k have values
boolean multiple;
if (i % k == 0)
{
multiple = true;
}
else
{
multiple = false;
}
AND and OR
• Used for combining conditions
• Use brackets to make sure compound expressions
mean what you want them to mean.
• Anywhere our pseudocode language calls for a
"test" you may use ANY Boolean expression
• What is the value of the following expressions?
((room = STE0131) OR (room = STE2052)) AND (Lab = ITI1220)
TRUE
(I am at home) OR (I am in the office)
TRUE
(I am at home) AND (I am in the office)
FALSE
Boolean Expressions:
• Write a test that returns TRUE if x is
between 10 and 20 (inclusive); the test
should return FALSE otherwise
Algorithm:
Java:
X  10 AND
X  20 ?
false
inRange 
FALSE
true
inRange
 TRUE
// assume x has a value
boolean inRange;
if ( (x>=10) && (x<=20) )
{
inRange = true;
}
else
{
inRange = false;
}
AND versus OR
• In the last slide:
– We used: ((x>=10) && (x<=20)) to
test whether x is between 10 and 20.
• What if we used OR || instead of
AND &&
– Suppose x is 7.
– If we had ((x>=10) || (x<=20)):
x<=20 is TRUE, and so the entire expression
is TRUE: but x is not between 10 and 20.
Boolean Expressions
• Write a test that is TRUE if B's value is in
between A's value and C's value (but, we don't
know whether A is bigger than C or vice versa).
Algorithm:
Java:
(((B  A) AND (B  C ))
OR
((B  C) AND (B  A)))
false
true
if (((b>=a) && (b<=c)) ||
((b>=c) && (b<=a)))
{
// b is between a and c
}
else
{
// b is outside range
}
Example 2
int i = 10, j = 15, k = 20;
double x = 10.0, y = 3.333333, z = 100.0;
Compute the following logical expressions
i < j || j < k && x <= y
(i / 3) == y
(x / 3) == y
!(x != i)
10
Example 3
Suppose X = -1 and Y = 5.
Expression
(X > 0) AND (NOT (Y = 0))
(X > 0) AND ((X < Y) OR (Y = 0))
(NOT (X > 0)) OR ((X < Y) AND (Y = 0))
Value
TRUE
TRUE
FALSE
NOT ((X > 0) OR ((X < Y) AND (Y = 0)))
FALSE
Can you translate them to Java syntax?
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Exercise 4
• Write a Boolean expression that evaluates true
if the age is between 18 and 55 inclusively.
– Develop a problem solving method with one parameter
(GIVEN), the age, and a boolean result – true if age is
in the interval and false otherwise.
– Complete the program with a main method that
request an age from the user and prints “Transaction
accepted” if the age is within the interval and
“Transaction refused” otherwise.
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Exercise 5
• Write a program that checks for an integer
number if divisible by 2 and/or 3. The
program should use the two methods
template:
– The main method should interact with the user
to get the value of the integer and displays if
this integer is divisible by 2 and 3.
– The isDivisible method has one parameter
(GIVEN) the value of the number and one result,
an integer representing if the number divides 2
and 3, divides 2 or 3, or doesn’t divide both.
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Example 6
• Design the algorithm that receives an
integer number and returns -1 if the
argument is less than zero, returns +1
if the argument is greater than zero
and returns zero if the argument is
zero.
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Exercise 7
• Translate the following algorithm to Java
GIVEN:
INTERMEDIATE:
RESULT:
HEADER:
BODY:
(none)
Grade
(none)
LetterGrade()