"Java" java_06 basic data types

1. Basic data types

Java is a strongly typed language, and each variable must declare its type.

. Java 's data types fall into two main categories: the base type (primitivetype) and the reference type (reference type )  

. 3 classes of 8 Basic data Types are defined in Java

. Logical Type-Boolean

. Text Type- Char

. Numeric Type- byte, short, int, long, float, double

Note: The size of the reference data type is uniformly 4 bytes, and the address of the reference object is recorded!

2. Integer variables

An integer is used to denote a numeric value without a decimal part, which allows a negative number.

scope and operation of integral type Java the code is machine-independent, which is exactly Java One of the reasons why the program has a strong transplant capability.

Type	Occupy Storage space	Table Count Range
Byte	1 bytes	-128~127
Short	2 bytes	-215 ~ 215-1 (-32768~32767)
Int	4 bytes	-231 ~ 231-1 ( -2147483648~2147483647) about + billion
Long	8 bytes	-263 ~ 263-1

three representations of the Java-language integer constants:

decimal integers, such as:-500, 0.  

an octal integer that requires a 0 start, such as:015.  

hexadecimal number, requires 0x or 0X beginning, such as:0x15 .

the integer constant for the Java language defaults to type int , declaring that a long constant can be followed by an ' l ' or ' L ' , such as:

Long a = 55555555; no error, within the range of Int ( within billion ).

Long B = 55555555555;// does not add an error, it has exceeded the range represented by Int. Error:

The literal 55555555555 of type int is out of range

There is no unsigned type in Java

3. Code hinting

 Public classtestdatatype{ Public Static voidMain (string[] agrs) {intA = 100;//default is 10 binary number        intb = 010;//8 binary        intc = 0x10;//16 binarySystem.out.println (a);        System.out.println (b);                System.out.println (c);  System.out.println (Integer.tobinarystring (a)); //convert to 2 binarySystem.out.println (Integer.tooctalstring (a));//Convert to 8 binarySystem.out.println (Integer.tohexstring (a));//convert to 16 binary        byted = 100;//if the size of the data does not exceed Byte/short/char's stated range, it can be automatically transformed        LongE = 11123213232L; }}

"Java" java_06 basic data types