1. INTERMEDIATE PROGRAMMING USING JAVA
CS-0401
INTERMEDIATE PROGRAMMING USING JAVA
Prof. Dr. Paulo Brasko Ferreira
Fall 2016
© – All Rights Reserved

2. The While Loop
© – All Rights Reserved

3. Store data via Identifiers and Variables
Get data in
Your program
Control Structures
Get data out
Statements and
Expressions
© – All Rights Reserved

4. Control Statements Linear Execution Conditional Execution
Iterative Execution
© – All Rights Reserved

5. The While Loop A Real-life example of WHILE loop
2012 Presidential Towers Stair Climb Video (
© – All Rights Reserved

6. The While Loop While Loop Syntax: Example:
while(boolean condition is true) {
execute commands inside }
Example:
int currentFloor = 10;
int topFloor = 50;
while(currentFloor < topFloor) {
System.out.println(“Almost there! Floor: “ + currentFloor);
currentFloor++;
System.out.println(“Finally here! Top floor!”);
© – All Rights Reserved

7. Pay attention to infinite loops
While Loop
Pay attention to infinite loops
int number = 0;
while (number <=5); {
System.out.println(“Hello”);
number++; }
What is wrong here ?
© – All Rights Reserved

8. While Loop – A Simple Program
Program main tasks:
User will enter some scores
After all the scores have been entered, it computes the average value
flow diagram
(In)valid scores
When to stop collecting #s?
How to compute average?
significant digits?
How to keep the # of entries?
© – All Rights Reserved

9. Solutions for the program
Possible implementations for this problem
Ex5a.java
Ex5b.java
Remember Grasshopper: there are many possible ways to go through a forest full of trees…
© – All Rights Reserved

10. The Do-While Loop
© – All Rights Reserved

11. The Do-While Loop Syntax:
statement(s);
} while (condition);
Example:
int number = 5;
Scanner scan = new Scanner(System.in);
int numberOfGuesses = 0;
System.out.println(“Enter your guess: ”);
int userGuess= scan.nextInt();
if (number != userGuess) {
System.out.println(“Sorry, wrong number! Try again!”); }
numberOfGuesses++;
} while (number != userGuess);
© – All Rights Reserved

12. The “Conventional” FOR loop
© – All Rights Reserved

13. Control Statements Linear Execution Conditional Execution
Iterative Execution
© – All Rights Reserved

14. See forexamples.java, ex5c.java, ex5d.java
The for Loop
The for loop takes the form:
for(initialization; test; update) {
statement(s); }
Example:
int maxNumber = 5;
for(int i = 0; i < maxNumber; i++)
System.out.println(“The square of “ + i + “ is “ + i*i);
See forexamples.java, ex5c.java, ex5d.java
© – All Rights Reserved

15. Nested Loops
© – All Rights Reserved

16. Nested Loops Example: for(int i = 0; i < 3; i++)
for(int j = 0; j < 4; j++)
loop statements;
Let’s generate the following 2D matrix
© – All Rights Reserved

17. The “Enhanced” FOR loop
© – All Rights Reserved

18. The enhanced for Loop The for loop takes the form: Example:
for(type tempVar : listOfVariables){
statement(s); }
Example:
int[] listOfGrades = { 5, 10, 8, 6, 2};
int sum = 0;
for(int grade : listOfGrades) {
sum += grade;
double avg = sum / listOfGrades.length;
© – All Rights Reserved

19. Interviewing marathon runners
For all people walking
on the street
If it is a runner, then interview
If it is not a runner, then skip to the next person walking
Do I know how many people will pass?
Do it until the race starts
So I’ll use the While loop for it!
Emergency Stop Interviews
© – All Rights Reserved

20. update while condition
// start // reporter greets the TV viewers boolean raceHasStarted = false; while(!raceHasStarted) { if (isARunner()) { performInterview(); } else { continue; // let’s talk about this if (isThereAnEmergency) { break; if (currentTime == raceStartTime) { raceHasStarted = true; // finish // reporter gives her final remarks.
Start
while (condition)
Is a runner?
Interview runner
Any emergency?
Stop Interviewing
update while condition
Finish
© – All Rights Reserved

21. Syntax Errors Logic Errors Run-time Errors
© – All Rights Reserved

22. double pi = 3.1415, volume, ratio; // or we can use Math.PI
// computig the volume of a sphere V= 4/3*PI*Radius^3
double pi = , volume, ratio; // or we can use Math.PI
double radius = keyboard.nextDouble();
// computing the volume
volume = 4/3 * pi * Math.pow(radius, 3); // logic error here
// computing ratio between volume and radius
ratio = volume / radius; // potential run-time error
// computing ratio square
double ratioSquare = ratio * raito; // syntax error
if (ratioSquare == 3.0) { // logic error, why?
// some code here }
© – All Rights Reserved

23. Coding errors
Syntax Errors: easy to spot either during typing (if you are using an IDE) or during compilation time.
Logic Errors: sometimes very hard to find. The use of debugging tools inside an IDE can help your task in finding the problem.
Run-time Errors: As a developer you must think what could go wrong and try to circumvent it with internal checks in your code before using the data (IF statements, Exceptions, etc)
© – All Rights Reserved

24. Any Questions?
© – All Rights Reserved