Variables and Types

Type	Size	Range
boolean	depends	true, false
char	2 bytes	Unicode characters
byte	1 byte	[-128, 127]
short	2 bytes	[-32768, 32767]
int	4 bytes	[-2147483648, 2147483647]
long	8 bytes	[-9223372036854775808, 9223372036854775807]
float	4 bytes	[-3.4E38, 3.4E38]
double	8 bytes	[-1.7E308, 1.7E308]

Source: Drozdek, A. (2013). Data structures and algorithms in Java. 4th ed. Singapore: CENAGE Learning.

• Unlike C++, Java has a boolean type which does not support numeric operations

Declarations

<type> <name>

Examples:

int myInt = 5;

boolean myBool = false;

char capitalC = 'C';

// Floating-point literals are 64 bit by default, therefore
// needs to be cast for `float` type
float myFloat = 45.64f;
float myFloat = (float) 46.64;

Wrapper Classes

The above data types are Primitive Data Types, they are the only types that are not Objects.

Many classes in the java.util package operate on Objects such as Integer and Boolean. Note that the Java platform will box the primitive type in its wrapper class for you when a method expects an Object. Similarly it will unbox the Object if a method expects a primitive. See Autoboxing and Unboxing.

There are some cases when you want to use an Object instead of a primitive:

• When converting between numbers and strings

  Integer myInt = 5;
  String myString = myInt.toString();
  
  Integer MyInt = Integer.parseInt("5");
  

• When a method expects an Object

Primitive type and corresponding wrapper class:

Primitive type	Wrapper class
boolean	Boolean
byte	Byte
char	Character
float	Float
int	Integer
long	Long
short	Short
double	Double

Further Reading (Optional)

• The Number Classes
• Autoboxing and Unboxing