Transcript Chapter 5 Program Structures

Chapter 5
Program Structures
5
Branching
Allows different code to execute based
on a conditional test.
if, if-else, and switch statements
5
If, Else, and Else-If
if Statements
“If the sky is blue, I’ll ride my bike.”
else Statements
“If the sky is red, I’ll drive; else
(otherwise) I’ll ride my bike.”
Else-if Idioms
“If the sky is blue, I’ll ride my bike; else if
the sky is red, I’ll drive, else I’ll walk.”
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Nested if Statements
if statements can be nested
(combined) within other if statements
to account for multiple conditions.
If the sky is blue
If there are clouds in the sky
Do something for blue sky, cloudy days
Else
Do something for blue sky, cloudless days
Else
Do something for non-blue sky days
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The switch Statement
switch statements are an efficient
way to choose between multiple
options.
Easier to expand options than else-if
structures
Easier to read than multiple else-if
structures
Use the break keyword to prevent “falling
through” to next statement
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Switch Evaluation
switch statements evaluate int values:
int x = 3;
switch(x)
{
1:
x += 2;
break;
2:
x *= 2;
break;
3:
x /= 2;
break;
}
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Logical Operators
Combine or negate conditional tests
Logical AND (&&)
“The value of x is greater than 10 and the value of x is less
than 20”
(x > 10) && (x < 20);
Logical OR (||)
“The value of x is greater than 10 or the value of x is less
than 5”
(x > 10) || (x < 5);
Logical NOT (!)
“The value of x is not greater than 10”
! (x > 10);
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Looping
What is iteration?
Iteration is a structure that repeats a
block of code a certain number of times,
or until a certain condition is met.
5
The while Loop
“As long as this condition is true,
execute this code”
while ( counter < 11)
{
counter++;
}
Might not execute if the condition is
already false
5
The for Loop
Includes (optional) arguments for:
An initialization variable
A conditional test
An action
for ( int counter = 1;
counter < 11; counter++ )
{
System.out.print(counter + “ ”)
}
5
The do...while Loop
“Take this action, while this is true”
int value = 10;
do
{
value = value + 2;
}
while ( value < 10 );
Ensures at least one execution of code