JAVA

Lesson 1: Variables and Data Types

Basic

System.out.println();

• System —> System command
• Out —> output
• Println —> print a line

1. Java is case sensitive
2. Quotation marks display the message as is
3. Semi-colon means end of statement

Variables

Integer

/* Interger --> int */
int passengers; // declare
passengers = 0; // initialize
passengers = passengers +5;
passenger = passengers -3;
passenger = passenger -1 +5;
System.out.println(passengers); // answer is 6

• Also track multiple integers

String

String driver; //declare
driver = “Hamish”; //initialize
int letters = driver.length; // count length od the letter
System.out.println(letters); // answer is 6
driver = Driver.toUpperCase(); // change Capital letters to lowercase
System.out.println(driver); // answer is hamish

String driverFirstName;
driverFirstName = :Hamish”;
String driverlasgnarme;
driverLastName = “Blake”;

String driverFullName = driverFirstName + “ ” + driverLastName;
System.out.println(driverFullName); // answer is Hamish Blake

Variables name Rules

• Lower Camel Case ex)theFirstNames
  1. variable names are case sensitive
  2. start variable names with a letter
  3. cannot have white spaces

Types

Numbers

1. Integer int
2. Long
3. double

int maxInt = 2147483647;
long muchMore = 2147483647*10000000;
double fraction = 99.275;

Text

1. string
   1. use double quotension mark “ “
2. character
   1. use single quotention mark ‘ ‘
   2. accept only one character

      String fullText = “(b) WILL ended 1945”;
      char answer = ‘b’;
      char three = ‘3’;
      char ten = ’10’; //wrong
      

Decision

1. Boolean

   boolean fact = true;
   boolean fact = false;
   

   Arthmetic

2. adiition
3. Subtraction
4. Multiplication
5. Division

int x = 2+3; // 5
int y = 4-5; // -1
int days = 7*4; // 28
double div = 5/2; // 2
double accurate = 5/2.0; // 2.5

• the order of operation
  1. multiplication and division
  2. Addition and Subtraction
  3. if in doubt, use parntheses ()

I’m studing a “Java Programming Basics” @Udacity.

2019-01-07 12:00