Java Basic data types

1. Data type classification

2. Basic data types

3. Integer data type

A. Basic Concepts

Int x=0;

Allocate 4 bytes of memory, one byte to 8 bits, value range 2 31 to 2 31

bytex=-12;

Allocate one byte, machine code

shortx=12;

Allocate 2 bytes, emphasizing type, using method (short) 12;

The long type is denoted by the suffix l

Long width=12l;

Allocate 8 bytes to 64 bits

B. Data overflow

public class Demo1 {
public static void Main (string[] args) {
int max=integer.max_value;
System.out.println ("Shaping Max:" +max);
System.out.println ("max+1:" + (max+1));
System.out.println ("max+2:" + (max+2));
}
}

Results:

Plastic max:2147483647
The max+1:-2147483648//value becomes the smallest
max+2:-2147483647//value becomes sub-smallest

Workaround:

int max=integer.max_value;
System.out.println ("Shaping Max:" +max);
System.out.println ("max+1:" + (max+1));
System.out.println ("max+2:" + (max+2l));
System.out.println ("max+2:" + ((long) max+2));

If this is a Long data type overflow, it cannot be resolved.

4. Character types

Constant: ' 123 ' A '! ' Hello

General use of Char declarations

Code:

Converting between characters and shaping
Char ch1= ' a ';
Char ch2=97;
System.out.println (ch1+ "---" +ch2);

Commonly used escape characters:

Code:

Char chinaword=' good ',japanword='? ';

Char you =' \u4f60 ';

int position= 20320;

System. out. Print (" Kanji:" +chinaword+ " position:"+ (int) Chinaword);

5. Floating-point types

Float type

Must have F or F in the back, usually 8-bit valid data reserved

Allocate 4 bytes

Double type

Suffix d or D after, can be omitted

Allocate 8 bytes

float num=3.0f;
System.out.println ("num*num=" +num*num);

6. Boolean type

Constant: True, False

Variable: bool on=true;

Code:

Boolean flag=true;
SYSTEM.OUT.PRINTLN (flag);
System.out.println (!flag);

7. Default values for data types

Role: Sometimes there are variables in the Java program that are not assigned, which makes sense, and defines the default values to prevent this from happening.

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Java Basic data types