Java Basic program Design structure "3"

Data type

　　In Java, there are 8 basic types (primitive type), with 4 integer ,2 floating-point types , and1 character types used to represent Unicode-encoded character cells Char and 1 boolean types that are used to represent truth values (Boolean types).

　　1. Integral type

Type	Storage requirements	Range of values
Int	4 bytes	-2 147 483 648 ~ 2 147 483 647 (just over 2 billion)
Short	2 bytes	-32 768 ~ 32 767
Long	8 bytes	-9 223 372 036 854 775 808 ~ 9 223 372 036 854 775 807
Byte	1 bytes	-128 ~ 127

　　The long integer value has a suffix of L(e.g. 4000000000L). The hexadecimal value has a prefix of 0x(such as 0xCAFE). Octal has a prefix of 0, in order to avoid confusion, as little as possible with the octal system.

Note that Java does not have any unsigned type (unsigned).

2. Floating-point types

Type	Storage requirements	Range of values
Float	4 bytes	Approx. ±3.402 823 47E + 38F (6 to 7 digits of effective digits)
Double	8 bytes	Approximately ±1.797 693 134 862 315 70E + 308 (valid digits are 15 bits)

　　A value of type float has a suffix f (for example, 3.14F). A floating-point value with no suffix f (such as 3.14) defaults to the double type. Of course, you can also add a suffix D after a floating-point value (for example, 3.14D).

　　All floating-point numeric calculations follow the IEEE 754 specification. The following are three special floating-point values used to represent overflow and error conditions:

Zheng Infinity
Negative infinity
NaN (not a number)

　　3.char type

　　The char type is used to represent a single character. Typically used to denote character constants. For example: ' A ' is a character constant encoded as 65. Unlike "a", "a" is a string that contains the character a. Unicode encoding units can be represented as hexadecimal values, ranging from \u0000 to \UFFFF. For example: \u2122 represents a registration symbol (TM), and \u03c0 represents the Greek letter p.

In addition to the escape sequence character \u, which represents the encoding of a Unicode code unit, there are also escape sequence characters for special characters, see table 3-3. All of these escape sequence characters can appear in a character constant or in the quotation marks of a string. For example, ' \u2122 ' or ' hello\n '. The escape sequence character \u can also appear outside the character constant or the quotation marks of a string (while all other escape sequences may not).

　　4.Boolean type

　　A Boolean(Boolean) type has two values: false and True, which are used to determine the logical condition. an integer value and a Boolean value cannot be converted to and from each other .

Java Basic program Design structure "3"