Java basic data type, java Data Type

Java basic data type, java Data Type

1. Data Type Classification

2. Basic Data Types

3. Integer Data Type

A. Basic Concepts

Int x = 0;

4 bytes of memory are allocated. one byte occupies 8 bits. The value ranges from-2 to the power 31 to the power 1 of 2.

Bytex =-12;

Allocate one byte, machine Encoding

Shortx = 12;

Allocate 2 bytes. When the type is emphasized, use method (short) 12;

The Long type is indicated by the suffix L.

Long width = 12L;

Allocate 8 bytes to 64-bit

B. Data Overflow

Public class Demo1 {
Public static void main (String [] args ){
Int max = Integer. MAX_VALUE;
System. out. println ("integer max:" + max );
System. out. println ("max + 1:" + (max + 1 ));
System. out. println ("max + 2:" + (max + 2 ));
}
}

Result:

Integer max: 2147483647
Max + 1:-2147483648 // The value is minimized.
Max + 2:-2147483647 // the minimum value

Solution:

Int max = Integer. MAX_VALUE;
System. out. println ("integer 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 the LONG data type overflows, the problem cannot be solved.

4. Character Type

Constant: '000000' 'A ''! ''Hi'

Generally, char declaration is used.

Code:

// Conversion between character and integer
Char character = 'a ';
Char ch2 = 97;
System. out. println (Bytes + "---" + ch2 );

Common escape characters:

Code:

CharChinaWord = 'ha ',Japan= 'Signature ';

Char You= '\ U4f60 ';

Int Position= 20320;

System.Out. Print ("Chinese Character:" + chinaWord + "Location:" + (Int) ChinaWord );

5. Floating Point Type

Float Type

F or F must be followed. Generally, 8-bit valid data is retained.

Allocate 4 bytes

Double Type

The suffix d or D 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 Value of Data Type

Purpose: Sometimes variables with no value assignment exist in java programs, which makes sense useless and defines default values to avoid this situation.

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