Data types in Java

data types in Java

I. BASIC data Types

1. Basic data types

That is, int,char,float,double,byte, Short , Long , Boolean There are 8 types of such numeric values .

Data type	Number of digits	Range of values	Description
Byte	8	-128~127	The most primitive form of data stored in memory
Short	16	-32768~32767
Int	32	-2^31~2^31-1
Long	64	-2^63~2^63-1
Float	32	Slightly
Double	64	Slightly
Char	16	'\u0000'~'\uffff'
Boolean	1	True/false

2. Conversion of basic data types

(1) automatic type conversion is also called implicit type conversion;

When you assign a variable of one type to a variable of another type, an automatic type conversion occurs whenever the following conditions are true:

Mutual compatibility between the two types;

The target type is greater than the source type (that is, type promotion).

Such as:

char ch = ' A ';

int num = ch;

float f = num;

Double d = f;

type conversions occur automatically, without explicit instructions

(2) cast type

Coercion type conversions are also known as explicit type conversions;

If the data type of the converted value is greater than its target type, some information will be lost;

Such as:

int x = 65;

char ch = x;

Such statements will cause an error because the char type is less accurate than the int type, and the compiler cannot convert it automatically, only cast:

int x = 65;

char ch = (char) x;

Ii. type of reference

1. reference type data definition

Reference type except for the base data type

include classes in the API, such as String,File

Also includes custom classes, such as PersonalAccount,creditaccount

include arrays , such as int[],string[].

2. Scenarios used by reference types

Used as a type of attribute;

Used as the return value type of the method;

Used as the form parameter type of the method;

3. assignment of reference data types

Reference types are objects, so assignments are assigned using the new call construction method.

Exception: The String class can use the = assignment directly, without using new.

Three, the difference between the basic type and the reference type

	Basic data types	Reference data type
Concept	Variable (simple value)	Object (Reference)
Storage location	To store values in the stack	Save references in stacks, store property values for specific objects in the heap
How to assign a value	Direct Assignment	New ,String class and wrapper class can be directly assigned values

Data types in Java