3.3 Basic data types

3.3 Basic data types

Overview: In Java, there are 8 types of data, 6 of which are numeric types, the other two are character types and Boolean types, 4 of 6 numeric types are integer types, and two are floating-point types.

Basic data types

3.3.1. Numerical type

{

1, Integer type {byte;short;int;long}

2, floating-point type {float,double}

}

3.3.2. Character type

3.3.3 Boolean type

3.3.1 Numerical type

3.3.1.1 integer type

1. Byte

Memory Space: 8 bits 1 bytes (8 bits equals one byte), value range -128~127.

< problem >byte X=48,y=08,z; Defines the byte-type variable x, Y, Z, and assigns it to X, Y.

2.short: Short-integer

Memory space: 16 bits 2 bytes; value range -32768~32767

3.int: Shaping

The memory space is 32 bits and 4 bytes, and the value range is the most widely used in general.

In Java, the system default shaping is int.

< problem >int X=450,y=-463,z; define int type variable x, Y, Z, with initial value to X, y

4.long: Long Plastic

Memory space 64 bits 8 bytes;

A long variable must have an L or L at the end of the assignment, or the system will not recognize it. L is recommended because L and 1 are easy to confuse.

< problem >long X=123489861684265865965l;y=7896545236842659864l;z; Define a long variable x, y, z, and attach an initial value to X, y

Practice

3.3.1.2 floating-point types

Floating-point types represent numbers with fractional parts, in Java, and are divided into {1. single-precision floating-point decimals (float)

2. Double-precision floating point decimal (double). }

1. Single-precision floating point fractional float:

Memory Space: 32 bits 4 bytes; You must use F or f at the end of the assignment to declare the assignment as a single-precision floating-point decimal. Otherwise the system thinks of the double type variable.

< >:float z=12.125f;y=-5.132f,z;//defines the float type variable x, Y, Z, with an initial value of X, y

2. Double-precision floating-point decimal double:

Memory Space: 64 bits 8 bytes;

In Java, the system default floating-point double,

When you assign a double value, you can use the suffix D or D, or no, no hard rules.

< questions >:d ouble x=1.3201d,y= 61.8526d,z9.3214,q; ;//define float type variable x,y,z,q, and attach the initial value to X, Y, Z

3.3.2 character types

Char is a character type that is declared using the Insert keyword to store a single character, and the system allocates two bytes of memory space. When defining a character variable, enclose it in single quotation marks, for example, ' s ' denotes a character, and only one character in a single quotation mark, more than a character type, or a string. The string is to be declared with double quotation marks "".

<;://Declare char type variable

Char x= ' a ';

Since the sort position of character A in the Unicode table is 97, the above statement is allowed to be written as:

Char x=97;

int z= ' a ';

System.out.print (z);//Output 97

System.out.print (x);//Output A

As seen above, there is a certain connection between char and Int. can be converted!!!!

Escape character

\DDD the characters represented by the octal data, such as \456

\dxxx the characters represented by the 4-bit hexadecimal, such as \0052

\ \ backslash Character focus

\ t Vertical tab focus

\ r Enter key

\ nthe line of focus

\b Backspace key

\f Page Change

3.3.3 Boolean type

Boolean will only feedback true and false, that is, to determine the authenticity.

< example >boolean b1=true,b2=false,b3; Defines the Boolean variable b1,b2,b3 and assigns the initial value to the B1,B2

3.3 Basic data types