1.00 Tutorial 2
Control Structures and Classes
Outline
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Take Attendance
Uploading Problem Sets
Control Structures
Simple Classes
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Control Structures
• List the control structures you have learn in
lecture.
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Control Structures (cont.)
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Lists of control structures:
–
–
–
–
if … else …
for loop
while loop
do … while loop
Control Structure Examples
if (a>5)
if (a<10)
b = 10;
else
b = 0;
else
b = -1;
When a is 15, what is b? How about when a is 6, what is b?
And when a is 0, what is b?
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A slight change
b = 7;
if (a>5) {
if (a<10)
b = 10;
}
else
b = 0;
If a=15, what is b? If a=0, what is b?
One more change
Now, remove the braces…
b = 7;
if (a>5)
if (a<10)
b = 10;
else
b = 0;
If a=15, what is b? If a=0, what is b?
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Answer
• Unless braces are used to explicity denote
which if clause is associated with an else
clause, the else clause is associated with the
nearest if clause that precedes it.
Readability of Code
• if (a>5)
if (a<10)
b = 10;
else
b = 0;
else
b = -1;
• b = 7;
if (a>5) {
if (a<10)
b = 10;
}
else
b = 0;
(aren’t these easier to read? On Forte,
you can do right click on your code
and choose reformat code)
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Loops
• How would you write a for loop that calculate the
sum of even numbers from 2 to 20?
• Can you use a while loop to do the calculation
instead?
• The three different kinds of loops are
interchangeable, but sometimes one is better than
the other. Do you know the differences?
Logical Operators
• Do you know what the follow operators mean?
– ==, &&, ||, !=
• What is the value of this expression:
(assuming c = 5, a = 2, b = 10)
c!=0 || a >= 10 && b < c*c/a
• What will happen when you compile the following code:
(assume x is –5)
if (x=0)
System.out.println(“x is 0!”);
else
System.out.println(“x is not zero. It is “ + x);
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Classes
• What do classes contain?
– Data (what kind of data can they have?)
– Methods
• Lets write a Rectangle class.
– What data fields do you think it should have?
– What methods might it have?
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