Primitive Types

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Primitive Types

• CSE 115
• Spring 2006
• April 3 7 2006

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Type

• A set of values and the operations we can do with
  those values.

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Object Types vs. Primitive Types

• We have been using object types all semester.
• Primitive types are another type built into Java.
• The distinction between these two types has been
  significantly blurred by Java 5.

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Primitive Types

• Primitive Types ? Objects
• The way we create them is different.
• Primitive types have a value.
• Objects have instance variables.
• Primitive types have operations we can perform on
  them.
• Objects have methods we can call on them.

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Types of Primitives

• Numbers
• Booleans
• Characters

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Numbers

• Whole Numbers
• byte 1 byte (-128 to 127)
• short 2 bytes
• int 4 bytes (-2147483648 to 2147483647)
• long 8 bytes

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Operations on Numbers (Unary)

• Promotes a byte, short or char to an int
• -
• Unary negation
• Increment
• --
• Decrement

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Operations on Numbers (Binary)

• Addition
• -
• Subtraction
• Multiplication
• /
• Division
• Modulus

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Important Note

• In Java, operations on integers are closed. This
  means that an operation performed on an integer
  returns an integer, or likewise, an operation
  performed on two integers returns an integer.

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More Numbers

• Real/floating point numbers
• float
• double
• Operations Same as for whole numbers

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Important note

• Operations on two real numbers return a real
  number.
• Operations on a real number and a whole number
  return a real number.

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How to get the real answer to the division of
two integers?

• Typecasting we can force Java to believe that
  we are doing floating point arithmetic.
• int a 1
• int b 2
• double realAnswer (double)1/2

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Booleans

• Two-valued algebra system
• True
• False
• The boolean values in Java are true and false
  (not 0 and 1).

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Operations that return boolean values

• lt
• Less than
• gt
• Greater than
• lt
• Less than or equal to
• gt
• Greater than or equal to
• Equals
• !
• Not equals

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Operations performed on booleans (Unary)

• Negation (not)
• Symbol !
• Meaning

p !p
true false
false true
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Operations performed on booleans (Binary)

• Conjunction (and)
• Symbol
• Meaning

• Disjunction (or)
• Symbol
• Meaning

p q p q
true true true
true false false
false true false
false false false
p q p q
true true true
true false true
false true true
false false false
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Short circuit boolean evaluation

• Java supports short circuit boolean evaluation.
• This means that if there is a false in a
  conjunction or a true in a disjunction, Java
  stops evaluating the expression and produces the
  result.

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Characters

• Single letter, digit, or symbol
• Character literals are surrounded by in code
• char aCharacter x
• Character class has methods of interest when
  working with characters.

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String

• Not a primitive type
• Sequence of characters
• String literals are surrounded by in code
• String greeting Hi there!

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String concatenation

• Can combine strings together using the
  operator.
• String one light
• String two house
• String result one two
• result now has the value lighthouse

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String concatenation

• You can also combine a string with a primitive
  type.
• int a 5
• int b 6
• int result a b
• String output The result of multiplying 5 and
  6 is result

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String Class

• There are many useful methods for String
  available in the String class.