Practice and
Evaluation
Practice
Develop a java class called:
SumCalculator.java
which computes a sum of all integer
from 1 to 100 and displays the result
to the screen
Problems with practice
exercise
• Problem solving skill:
– Recognize and understand problems
– Develop an algorithm
– Coding
• Java syntax
– Translate from algorithm to code
– Practice. Practice. Practice
Flowchart and Algorithm
- a computer is only a problem-solving
tool!
- Java is one tool used to solve
problems
Method of Problem
Solving
•
•
•
•
•
•
Recognize and understand the
problem.
Accumulate facts.
Select appropriate theory.
Make necessary assumptions.
Solve the problem.
Verify results.
Method of Problem
Solving
•
•
•
•
•
Develop an Algorithm.
Write the program in a computer
language. (i.e. in C, Java etc)
Enter the program into the
computer.
Test and debug the program.
Run the program, input data, and
get the results from the computer.
Algorithm and Flowchart
•
•
An Algorithm is just a detailed
sequence of simple steps that are
needed to solve a problem.
A Flowchart is a graphical
representation of an algorithm.
Algorithm
(Week 3 practice)
Develop a java class called:
SumCalculator.java
which computes a sum of all integers from 1 to 100
and displays the result to the screen
Step 1: Understand the problem:
Computes a sum of all integers from 1 to 100
Step 2: What is the input?
Start from 1, stop if reach 100 or (1 and 100)
Step 3: What is the output?
Sum
Algorithm
Step 4: How do we compute the output? (first solution)
Step 4.1: Start with the current integer: 1
Step 4.2: Sum starts with 0
Step 4.3: Add the current integer to Sum
Step 4.4: If the current integer is less than 100, keep
on adding the current integer to sum and increase
It by 1(i.e, go back to 4.3).
Step 4.5:Otherwise, print out the sum
Algorithm
Start
Sequential
steps
Stop
Condition/
Decision
Flowchart
Step 4.1: Start with the first integer: 1
Step 4.2: Sum starts with 0
Step 4.3: Add the current integer to Sum
Increase
Step 4.4: If the current integer is less
Current
than 100, go to next integer
Integer by 1
and keep on adding
the current integer to
sum (i.e, go back to 4.3).
Start
Current Integer=1
Sum=0
Sum = Sum +
Current Integer
Current Integer
< 100
Step 4.5:Otherwise, print out the sum
Print Sum
Stop
Practice
Step 4 (second solution):
sum = 100*(100+1)/2
Testing a program
• Ideal: Test cases should be designed
BEFORE writing the code
• Practice: Test cases are only
designed AFTER the code is written
Time to write codes <= Time to test
What should we test
• Philosophy:
– Test everything that could reasonably
break.
For example:
Test if the inputs received from a user is
valid
Test if the computation is done correctly
How to develop a test case
• A test case is a document that contains
- test case id
- description of what this test case is
- an input,
- an action, or event and
- an expected response
to determine if a feature of an application
is working correctly.
Example
• Test Case Id: Testcase01
Description: Testing if the program
exits when an invalid number of
weeks is entered
Input: an integer represents a
number of weeks and is outside of
[1..12]
Expected response: the program will
display a message and exit
Testing Amortization.java
• Please test the Amortization.java in
(c), (d) and (e) following the test
cases given
Practice
- Modify the existing SumCalculator.java
program to print out the average:
1 100
average 
i

100 i 1
Practice
• Develop a class called PrintEven to
print only even integers from 1 to 100
• Modify the existing PrintEven to print
only even integers from 1 to n. Allow
a user to enter the value for n.
Check list
• Make sure comments are included in
LoanCalculator.java
• Make sure that the directories are created,
classes and java files are copied
according to the requirements of the
project
• Make sure to copy the design document
• Email (zip files), or submit your project on
floppy disk or CD on time
Practice
• Write the code ComputeMin to print
out the minimum of three integers.
Three integers are inputs from a user
• Reuse the code ComputeMin to
develop ComputeMax which prints
out the maximum of three integers.
Three integers are inputs from a user
Practice
• Develop a class call PrimeNumber
that:
– Get an integer as input from users
– If the integer is a prime number, print
out a message that says: Prime number
– If not, print out a message that says: It
is not a prime number
Algorithm
• Run a for loop that tests to see if any
number from 2 up to sqrt(n) divides
evenly into the given number. If you
find one, then the number isn't prime.
If you don't find one, the number is
prime.