Basic data type and reference type

What are variables of basic data type?

A variable whose value itself is contained in the variable

Memory usage area for basic data type variables

The basic data types are the following eight types.

type Bit number Description
boolean 1bit true or false
byte 8bit Signed integer-128~127
char 16bit Unicode single character
short 16bit Signed integer-32768~32767
int 32bit Signed integer-2147483648~2147483647
long 64bit Signed integer about-922 Kyo-about 922 Kyo
float 32bit Floating point number
double 64bit Floating point number

Variables of the basic data type allocate the required memory area when defined. The value is assigned and held as it is in the secured memory area.

Suppose you execute the following code.

Basic data type


int x = 10;
int y = x;
y = 20;
System.out.println(x);
System.out.println(y);

The output is as follows.

output


10
20

In this way, the variable of the basic data type stores the value itself in the variable. Therefore, the content of y changes from 10 to 20, and 20 is finally output.

What is a reference type variable?

A variable that holds the location (memory address) where the value is stored, rather than storing the value itself. Unlike the basic data type, if you do not know what value will be assigned, you do not know how much memory area should be reserved. In addition, the memory area once reserved for the variable in the memory cannot be changed significantly later. Therefore, these reference variables are assigned code that indicates the location of the values created in other parts of memory. The code that indicates this location is called the reference value.

Suppose you run the following code.

Reference type


int a[] = { 1,2,3 };
int b[] = a;
b[0] = 2;
System.out.println(a[0]);

The output is as follows.

output


2

This is a characteristic part of the behavior of reference variables. Since the code stored in b [] indicates the location of ʻa [] , changing the contents of b [] changes the contents of ʻa [] at the same time. I will end up.

Referenced articles

https://nobuo-create.net/sanshougata/

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