Type
-
byte
,short
,int
,long
(integers)byte b = 1; // bytes are 8 bits long, [-128, 127] short s = 10; // shorts are 16 bits long, [-32,768, 32,767] int i = 20; // ints are 32 bits long, [-2^31, 2^31) long l = 30; // longs are 64 bits long, [-2^63, 2^63) // all are of 2's complement
float
,double
(floating numbers)float f = 10f; // single-precision 32-bit IEEE 754 floating point double d = 20.0; // double-precision 64-bit IEEE 754 floating point
String
,char
(Text)String s = "This is a string"; char c = 'G'; // this is a character // char can only be one letter long and uses single quotes
boolean
(true and false)boolean tf = true; // booleans designtes true or false
-
array (
T[] where T is the defining type of the array
)// creates an int array of size five filled with default values // in this case the default value of an int is 0 int[] arr = new int[5];
int[] arr
is[0, 0, 0, 0, 0]
To access a value in an array, an index is required.All array indices start at 0 and go up to the length of the array - 1
int[] arr = new int[5]; arr[0] = 1; arr[1] = 2; arr[2] = 3; arr[3] = 4; arr[4] = 5; System.out.println(Arrays.toString(arr)); // prints out the list in readable form, this is imported from java.util.Arrays
int[] arr
is now[ 1, 2, 3, 4, 5]
You can create an array of any type, just use
[]
after the type and it will become an array. i.e.int[] double[] byte[] String[] char[] boolean[]
reference: Basic Types and Arrays and Strings
All of the above types are known as primitives, except String
. Primitive types begin with a lowercase letter and are the types you’d expect a language to handle intuitively. However, they don’t have all the features of complex types like String
and ArrayList
, which you’ll learn about later. For this reason, Java has a workaround known as auto-encapsulation where it will automatically treat primitives like int
as complex wrappers like Integer
, and vice versa, depending on context.