Java Base 1_java data type

One. Java data types are divided into

1. Native data types

Also called basic data type, divided into shaping, floating-point type, character type, Boolean type. There are byte,short,int,long in shaping, floating-point type has float,double, character type has char, Boolean type has Boolean.

2. Reference data types

Includes class, interface, array

Two. Constants and variables

A constant is the amount of value that does not change, and a variable is the amount to which the value can vary.

Three. Declaration and initialization of variables

Example: int A;

a=0;

int b=0;

Four. Size of data type

In memory, the Byte,boolean type of data accounts for 1 bytes, or 8 bits;

The data of the Short,char type is 2 bytes, i.e. 16 2 binary bits;

The data of the Int,float type is 4 bytes, i.e. 32 2 binary bits;

The data for the long,double type is 8 bytes, or 64 2 binary bits.

Five. Type conversion

Type conversions are divided into forced type conversions and automatic type conversions.

When a type with a small precision is assigned to a variable with a high precision, it will be converted automatically, and the precision can be lost if the assignment of high precision to a variable with small precision requires forced type conversion.

Example: int i = (byte) 1; That's right

float a= 1; Correct, 1 The default is int type

float b=1.0; Error, 1.0 The default is double type, precision is higher than float, should be float b=1.0f;

int x = 5.5; Error, mandatory type conversion required, int x = (int) 5.5;

Java Base 1_java data type