1.2 Variables and Types

Read: http://www.learnjavaonline.org/en/Variables_and_Types

• This explains some data types that there are. Know them, but be aware that we use int, double, boolean, String most often.
• Java is a strong typed language, which means variables need to be defined before we use them.
• Learn how to assign a value to a variable
• You can concatenate (to combine) primitives to form a string, using the + sign

primitives:

• byte (number, 1 byte)
• short (number, 2 bytes)
• int (number, 4 bytes) <<<integer
• long (number, 8 bytes)
• float (float number, 4 bytes)
• double (float number, 8 bytes) <<<decimal number
• char (a character, 2 bytes)
• boolean (true or false, 1 byte) <<<logic

Extra knowledge: doing math

• int +,-,*,/ int => int
  • (note the divide: integer divided by interger will get the integer quotient! 13/4=3)
• int +,-,*,/ double => double
• double +,-,*,/ double => double

Objects

Think objects as...well, a real object!

Objects contain more stuff than primitives. For example, String is an object. Objects require a constructor to construct itself, like:

Car c = new Car("Honda", 2018);

String is an exception. You don't need the constructor. You just use the quotation mark.

"this is automatically a string"

We'll learn more about this in later chapter.

Do the exercise (print out: H3110 w0r1d 2.0 true )

When you are confident, try the quiz below.

(hey, no cheating!)

Quiz

Complete this quiz without any outside resource!

This will be graded!!!

Created: Dexin in mid-march 2018

Updated: Dexin, 12/5/18