Introduction to Programming (CPSC 124)
—Hobart & William Smith Colleges, Spring 2015
Class Notes—January 30, 2015
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Built-in (primitive) data types

double

values approximations of real numbers
literals -43.234,   3.2e14,   0.0,   3.1415928,   1e-9
operator + - * /
meaning addition subtraction multiplication division
See also float (less precise approximation of real numbers)


int

values Integer values between -231 and 231 -1
literals -435623,   -32,   -1,   0,   1,   2,   42,   90000
operators + - * / %
meaning addition subtraction multiplication integer division remainder
See also long (-263 ... 263 -1),   short (-215 ... 215 -1),   byte (-27 ... 27 -1)

NOTE: Remember that division on all integer types truncates any fractional part, rather than rounding. For example, 9/4 == 2, and 99/100 == 0.



Other Data Types

Here are some of the other data types built in to Java. We'll cover these over the next week or so.

boolean

values "yes" / "no"
literals true,    false
operators && || !
meaning and or (inclusive) not

comparisons (between numeric types), yielding boolean result
operator meaning true false
== is equal to? 1 == 1 1 == 2
!= is not equal to? 1 != 2 1 != 1
< is less than? 1 < 2 1 < 1
<= is less than or equal to? 1 <= 1 2 <= 1
> is greater than? 2 > 1 1 > 1
>= is greater than or equal to? 1 >= 1 1 >= 2


char

values Integer values between 0 and 255, used to represent characters
literals 0, 1, 2, 93, 'a', 'A', '2', '[', '$', '.', '\"', '\t', '\n'
operators (see int)
See also int ,   long ,   short ,   byte


(Sort of) built-in data types

String

values sequences of characters
literals "Hey there!",  "23",  ""
operators      +
meaning   string concatenation
note Note: String is a "mostly built-in" type, and we can think of it as such for the first few weeks of the class (until we get to Objects). As we will see, there is actually a great deal more to String values than what is described here


Arrays

values sequences of values, all of the same type (including other arrays)
literals None. However, there is a literal initialization form, usable in declaration of an array variable (and not otherwise):
int[] A = {2,3,5,7,11,13}
operators      A[i]      A.length
meaning   access the ith element of A   number of elements in A
note An array with n has indices 0 ... (n-1). Arrays, like String values, are really objects. They, too, have some features of primitive types.

John Lasseter