Introduction to primitive data types.

Objectives

1. List the basic or primitive data types in Java
2. Describe what each type holds.

Notes

• In the book, this is section 2.2.2 Types
• In java there are 8 primitive types of data.
  • They are called primitive because they are the most basic types available.
  • Other types are constructed from these types.
  • They are the building blocks.
• Four are integer types.
  • An integer is a counting number, zero or the negative of the counting numbers.
    • Just like math, ... -3, -2, -1, 0, 1, 2, 3, ...
    • But we don't have the ... in programming.
    • Our memory is limited, so we have maximum and minimum values we can store.
  • We give different amounts of storage for different integer types.
    • Think about score boards.
      • Football scoreboards have two digits
      • Thus scores between 0 and 99 can be represented.
      • Basketball scoreboards have three digits
      • In this case scores between 0 and 199 (or 999) can be represented.
    • The number of digits determine the range.
  • For memory we store data in bits (0 or 1) or bytes (8 bits)
  • Integer types
    • byte holds 8 bits, or -128 to 127
    • short holds 16 bits or -32,768 to 32,767
    • int holds 32 bits or -2,147,483,648 to 2,147,483,647.
    • long holds 64 bits or -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
    • In general, unless you have a reason, use the type int
• Floating point numbers, or floats, are numbers
  • with a decimal point 3.14159
  • or in scientific notation 6.023x10²³
  • There are two floating point types
    • float
    • double
  • Floating point numbers are a bit more complex
    • The suffer from round off error.
    • We will discuss this later.
• Other types
  • A char
    • Is a character.
    • This is anything in Unicode.
    • For now think
      • letter: a, b, c
      • single digits: 0, 1, 2, 3
      • Symbols: $, &, ,
      • Anything you can type
    • But there are more things.
    • Normally we put characters inside of ' marks ('a')
    • Some are escaped
      • '\n' is the newline character
      • '\t' is the tab character
    • eventually a collection of characters is called a string
      • These are inside " ("Hello World!")
      • We have seen these
      • We will talk about these again in the future.
  • A bool is a boolean value
    • Only two values, true or false.
    • We will use these extensively when we start decisions and looping.