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1323Agenda3
HW
int number = 716;
System.out.println(“The number is “ + “number”);
Valid variable name? two_shoes
Flowchart symbols and clarity. “Single entry point, single exit” for I/O, computation/process
Lab2
Good work – Continue to bring the kitchen sink to lab.
I’m hiring 3 new people:
1 to convert code to flowchart (like last class quiz)
1 to convert flowcharts to code
1 to develop flowcharts
String objects
String fname = “Jill”;
How ‘long’ is fname? How many characters in fname?
Sure, you just counted them – 4
String objects
String fname = “Jill”;
How ‘long’ is fname? How many characters in fname?
Sure, you just counted them – 4
String someLets = “asfgiopawrth8[w gae[gnklasdfga[r 9awe[rgklr 890S_yS nawoguS IS GiOPGIOS{G jIG imn{ Gjio[ SGJi{SiSgj()S{ GJ9S gj[ adfg9pa GUUV(_ “;
How long is someLets?
String objects
String someLets = “asfgiopawrth8[w gae[gnklasdfga[r 9awe[rgklr 890S_yS nawoguS IS GiOPGIOS{G jIG imn{ Gjio[ SGJi{SiSgj()S{ GJ9S gj[ adfg9pa GUUV(_ “;
How long is someLets?
Good news – java gives us a tool that tells us. A method called ‘length’.
How do we use it?
int len = 0;
len = someLets.length();
That looks something like num2Sqrt = Math.sqrt(num2);
Yes, they are both ‘Method calls”.
Review
To obtain user input from the terminal:
1 import java.util.Scanner;
2 Scanner console = new Scanner(System.in);
3 gpa = console.nextDouble ( );
Example: (after having 1 and 2 in your program:)
double num1 = 0;System.out.println (“Please enter a number: “);num1 = console.nextDouble( ):
Sample
Flowchart
Logic error, symbol error!
if – else construct
if (newRate > oldRate) {
cost = price * newRate; System.out.println(“New cost is “ + cost);
}
else
{
cost = price * oldRate; System.out.println(“No change to cost. Cost is “ + cost);
}
Note the use of the concatenation operator +
What is the “TRUE Block” “FALSE Block”
Note the indention of ‘subservient code’
Note that an if does not require an else.
if ( code > oldCode) {
System.out.println(“Code has changed. New code: “ + code);
}
System.out.println (“Hello Joe”);
Now I’ll put some examples on the board to try to trick you
Pick a num1:
if (num1 > 5)
System.out.println(“Joe”);
else
{
System.out.println(“Sarah”);
System.out.println(“Alice”);
num1 = num1 + 1;
}
System.out.println(“Henry”);
// ------------------------------------------------------------------
if (num1 > 5)
System.out.println(“Joe”);
else
System.out.println(“Sarah”); System.out.println(“Alice”);
num1 = num1 + 1;
System.out.println(“Henry”);
Pick a num1:
if (num1 > 5)
System.out.println(“Joe”);
System.out.println(“Alice”);
else
{
System.out.println(“Sarah”);
System.out.println(“Alice”);
num1 = num1 + 1;
}
System.out.println(“Henry”);
// ------------------------------------------------------------------
if (num1 > 5)
System.out.println(“Joe”);
else
System.out.println(“Sarah”);System.out.println(“Alice”);
num1 = num1 + 1;
System.out.println(“Henry”);
Subservient code.A standard practice is to indent subservient code consistently. At Dell, it is 2 spaces, Google, 4 spaces
if (num1 > 5)
{
num1 = num1 * 7;
num2 = 9;
}
else
{
num2 = 0;
}
Notes: { on line by itself
else on line by itself
Nested if statements
if (num1 > 5)
{
if (num2 == 4) {
num1 = num1 * 7;
num2 = 9;
} else
num1 = 5; }
else
{
num2 = 0;
}
Let’s work on lab 3
Note: Answering questions in the lab:
Read the lab at least 5 times.
Complete flowcharts for the program that you are working on. (it doesn’t have to be perfect, but it does have to be complete)
What is a “workbench box” in a flowchart? (think chocolate chip cookies)
Every method has its own flowchart.
Every program and system have their own Block Diagram
lab 3
seuCalculator has one method - main
seuController will have several methods, main, calculator, analyzeSentence, dieRoll and moneyBags
main is a ‘controller’ method – s/he will just tell other people what to do.
The calculator method will end up being your seuCalculator program logic
So we will put several methods in one class?
lab 3
How will we do that?
First things first – we already have a flowchart for calculator, so we just need a flowchart for
seuController main method
Here we go ----
lab 3
How will we do that?
Did we get here on Tuesday?
If so, roll on.
int num1 = 3;
System.out.println(“Hello “ + num1 + “ cats”);
System.out.print(“well, “);System.out.println(“well.”);
System.out.println(“So, let’s go \n” + “party!”);
Pop a new line - - how?, automatic?
Please Excuse My Dear Aunt Sally
Order of operations
(3*5 + 7) * 3/7 – 2
You can never have too many parentheses
Operators
== Equality operator (for primitive data types)
!=
>
>=
<
<=
|| or
&& and
Logical expression – an expression that is true or false universally
Truth Table
3 > 5 || today is Monday
A B A||B A&&B
!A A&&!B
T T T T F F
T F T F F T
F T T F T F
F F F F T F
Random numbers in java - book page 188(we will just use nextInt(xx) there are others)
1. import java.util.Random;
2. Random gener = new Random();
3. int num1 = 0;
Ex: num1 = gener.nextInt(7);
// integer 0, 1, 2, 3, 4, 5, 6
Ex: num1 = gener.nextInt(20);
// integer 0, 1, 2, …, 19
Ex: num1 = gener.nextInt(2);
// ?
Ex:
random integer between 4 and 13
we need rnum to be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13so 10 numbers. Note: 13 – 4 is 9 we need 9 + 1 = 10
How do we get 10 random numbers? nextInt(10)yes, but 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
But we want one of the 10 numbers 4, 5, 6, …, 13
Well, just add 4 to each of these numbers and ….So: rnum = gener.nextInt(10) + 4; does the job
Ex: generate a random integer between -3 and 3
