Week #2 Java Programming. Enable Line Numbering in Eclipse Open Eclipse, then go to: Window -> Preferences -> General -> Editors -> Text Editors -> Check.
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Slide 1
Week #2 Java Programming
Slide 2
Enable Line Numbering in Eclipse Open Eclipse, then go to:
Window -> Preferences -> General -> Editors -> Text
Editors -> Check Show Line Numbers
Slide 3
Simple Output For printing words (or Strings) onto the screen,
we use this command: System.out.println(Anything you want printed
here); If we want to print something that contains a variable, we
would use this command: String mySentence = Hey there.;
System.out.println(mySentence);
Slide 4
Simple Output String commands: \This represents a quotation
mark \This represents an apostrophe \nThis represents a new line
\\This represents a backslash \tThis represents a tab \sThis
represents a space
Slide 5
Simple Output Another way to print out text onto your screen:
This is used when you have a lot of variables to be included in the
print statement, example: String name = Vincent Tsang; int age =
60; String school = Binghamton University; System.out.format(My
name is %s, I am %s years old, I go to %s., name, age,
school);
Slide 6
Simple Output Printing out variables using the
System.out.println(); format: String name = Vincent Tsang; int age
= 60; String school = Binghamton University; System.out.println(My
name is + name + . I am + age + years old, I go to + school +
.);
Slide 7
If/Else Statements What is an if/else statement? Basically, in
programming, we will often have different ways to approach things
depending on the values given to it. We tell the program that If
something occurs, do this. If something else occurs, do something
else. Else do something else T his will be clearer when we write
out the code
Slide 8
If/Else Statements The command for the if/else statement is in
this format: if(comparison) { Something happens here; } else {
Something else happens here; }
Slide 9
If/Else Statements You are allowed to have more than one if
statement: if(comparison) { Something happens here; }
if(comparison2) { Something else happens here; } else { Something
else happens here; }
Slide 10
If/Else Statements Nested If/Else Statements: if(comparison) {
if(comparison2) {// Basically the same as && symbol
Something happens here; } } else { Something else happens here;
}
Slide 11
If/Else Statements Logical Operators || represents or This can
be found above your enter key (its located with the backslash)
&& represents and This can be found with the 7 key Switch
Statements This is used when you have a lot of things to compare
and do different type of commands This is to save time so that you
dont have to type out a billion if statements
Slide 12
If/Else Statements In a switch statement, we need a variable to
compare its value with: Example: int month;// This is our integer
variable switch(month) { case 1: System.out.println(January);
break; // We will always need to break out of the statement case 2:
System.out.println(February); break; } Do Exercise 1
(ExerciseOne.java)
Slide 13
Scanners What is a scanner? Scanner will ask user for an input
and store that input somewhere in the program to be used later
Scanners are not imported into java by default, you need to import
this yourself by using this command at the top of your code: import
java.util.Scanner;
Slide 14
Method Functions What is a method? A method is a collection of
statements that performs an operation Steps to do something, like
washing clothes you would first take your clothes out of the
hamper, then put it into the washing machine, then turn on the
washing machine, put in detergent etc. Function is another name for
Methods Remember that function/method names are always capitalized
except the first word. (Refer to Code Convention Format) Method
contains two parts Method header Method body
Slide 15
Method Functions Method Header (Signature for the method) The
heading that describes the method, example: public static void
sayHi() {// Method Header Code goes here;// Method Body } Another
Example (With return value): public static int getAge() { return
15; }
Slide 16
Method Functions with Parameters Same as before but this time
we will be using parameters, we use parameters when we need to give
the method outside information: Example: public static void
main(String[] args) { int age = 20; print(age); // This is a method
I created myself and not predefined by java } public static void
print(int age) { System.out.println(age); }
Slide 17
Operators What are operators? Operators are mathematical
symbols used to calculate numbers +, -, /, *, % +Addition
-Subtraction /Division *Multiplication %Modulus
Slide 18
Increment / Decrement operators There are commands for you to
increment or decrement numbers in a variable, for that we use ++ to
increment and we use to decrement, example: int counter = 0;
counter++;// This will add 1 to counter counter--;// This will
subtract 1 from the counter counter += 5;// This is the same as
counter = counter + 5; counter -= 5;// This is the same as counter
= counter 5; Things to remember: ++, --, +=, -=
Slide 19
Math Library Functions Like the scanner, the math isnt included
by default, we need to import it: import java.lang.Math; Commands
we can use from this library: AbsAbsolute Value PowPower
CeilCeiling FloorFloor MaxMaximum MinMinimum SqrtSquare Root
Slide 20
Math Library Functions How to use these functions: Absolute
value: int myInt = -5; int otherInt = Math.abs(myInt);
System.out.println(otherInt);// Will print out 5 Power:
System.out.println(Math.pow(otherInt, 2));
Slide 21
Math Library Functions Ceiling
System.out.println(Math.ceil(25.4)); Floor
System.out.println(Math.floor(37.9)); Maximum
System.out.println(Math.max(otherInt, myInt)); Minimum
System.out.println(Math.min(otherInt, 2));
Declaration String (Words/Sentences) String myVariable = Hello
World!; There are functions that are pre-made for strings which are
very useful: substring(int n) Returns everything after the n th
position including the one on n th position on a string
indexOf(String n) Returns the index of the string n on a string
isEmpty() Returns true/false depending if the string is empty
toLowerCase() Returns a string that is all in lower case
toUpperCase() Returns a string that is all in upper case
equals(String n) Compares one string to another
Slide 24
Declaration String functions examples: String myVariable =
Hello; Substring myVariable.substring(3);// Will return lo;
myVariable.substring(3,4);// Will return l;
myVariable.substring(0,2);// Will return ? indexOf
myVariable.indexOf(llo);// Return 2 isEmpty myVariable.isEmpty();//
Returns false