Introduction to java basic data types

There are two major data types in Java, namely:

• Built-in data types

• Reference data type

(Recommended tutorial: java introductory tutorial)

Let’s introduce them separately:

1. Built-in data types

The Java language provides eight basic types. Six numeric types (four integers, two floating point types), a character type, and a Boolean type.

1. byte:

byte data type is 8-bit, signed, integer expressed in two’s complement;

The minimum value is -128 (-2^ 7); The maximum value is 127 (2^7-1);

The default value is 0;

The byte type is used in large arrays to save space, mainly replacing integers, because byte variables occupy The space of the int type is only a quarter of that of the int type;

2. Short:

The short data type is a 16-bit, signed integer expressed in two's complement;

The minimum value is -32768 (-2^15); the maximum value is 32767 (2^15 - 1);

Short data type can also save space like byte. A short variable is half the space occupied by an int type variable;

The default value is 0;

3, int

int data type is 32 bit, signed integer expressed in two's complement;

The minimum value is -2,147,483,648 (-2^31); the maximum value is 2,147,483,647 (2^31 - 1);

General Integer variables default to int type;

default value is 0;

4, long

long data type is 64-bit, signed in binary Integer represented by complement;

The minimum value is -9,223,372,036,854,775,808 (-2^63); the maximum value is 9,223,372,036,854,775,807 (2^63 -1);

This type is mainly used when comparison is required On systems with large integers;

The default value is 0L;

5, float

float data type is a single-precision, 32-bit floating point number that complies with the IEEE 754 standard;

float can save memory space when storing large floating point arrays;

The default value is 0.0f;

Floating point numbers cannot be used to represent precise values, such as currency ;

6, double

double data type is a double-precision, 64-bit, floating-point number that complies with the IEEE 754 standard;

The default type of floating-point number is double type;

The double type also cannot represent precise values, such as currency;

The default value is 0.0d;

(Learning video recommendation: java course)

7, boolean

The boolean data type represents one bit of information;

has only two values: true and false;

This type is only used as A flag to record true/false conditions;

The default value is false;

8, char

The char type is a single 16-bit Unicode character;

The minimum value is \u0000 (that is, 0); the maximum value is \uffff (that is, 65,535);

char data type can store any character;

2. Reference type

In Java, reference type variables are very similar to C/C pointers. A reference type points to an object, and a variable pointing to an object is a reference variable. These variables are assigned a specific type when declared, such as Employee, Puppy, etc. Once a variable is declared, its type cannot be changed.

Objects and arrays are reference data types. The default value for all reference types is null. A reference variable can be used to refer to any compatible type.

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