"Crazy Java Handout" (v)----data types

A note

Single-line Comment://

Multiline Comment:/* */

Document Note:/**

*/

Because only public or protected-modified content is what you want to expose to others, and the API documentation primarily provides information to the consumer, JAVADAOC only handles public or protected-modified content by default. If the developer really wants the Javadoc tool to extract the contents of the private adornment, you can add the-private option when using the Javadoc tool.

The Javadoc tool does not extract information from the @author and @version two tags by default, and if necessary, you should specify-author and-version two options when using the Javadoc tool.

Two data types

• Base type (primitive type):

1. 1. Boolean type 1-bit
   2.     numeric type:
      1. integer 　 Type (default integer is int)
         1. byte 1 byte    -2^7 ~ 2^7-1
         2.       short   2 bytes   -2^15 ~ 2^15-1
         3.       int         4 bytes   -2^ ~ 2^31-1
         4.       long       8 bytes   -2^63 ~ 2^63-1
         5.       Char       2-byte
      2.       floating-point type (default floating-point number is double)
         1. float       4 bytes (the 1th bit is the sign bit, the next 8 bits represent the exponent, and the next 2 bits indicate the mantissa)
         2.      D Ouble    8 bytes   (The 1th bit is the sign bit, the next 11 bits represent the exponent, then the next 52 bits represent the mantissa)

• Reference type (reference type):
  1. Class
  2. Interface
  3. Array
  4. Null

• binary integers

The computer saves all integers in the form of a complement. Complement calculation rule: positive complement and the original code is exactly the same, negative complement is its anti-code plus one, anti-code is to the original code bitwise reverse, but the highest bit (sign bit) remains unchanged.

• Infinity

Positive Infinity: double.positive_infinity or Float.positive_infinity

Negative Infinity: double.negative_infinity or Float.negative_infinity

Non-number: Double.NaN or Float.nan

　　　　

All positive infinity values are equal, all negative infinity values are equal, and Nan is not equal to any numeric value, even to Nan.

Only the floating-point number divided by 0 can get positive infinity and negative infinity, because Java automatically treats divisor 0 as 0.0. However, if an integer value is divided by 0, an exception is thrown: java.lang.ArithmeticException:/by zero

eg

 Public classTestDate { Public Static voidMain (string[] args) {/** Date date = new Date (1474496229424L);         SYSTEM.OUT.PRINTLN (date); */        floatAF = 5.2345556f;        SYSTEM.OUT.PRINTLN (AF); DoubleA = 0.0; Doublec =double.negative_infinity; floatD =float.negative_infinity; System.out.println (c==d); System.out.println (A/a); System.out.println (A/A = =Float.nan); System.out.println (6.0/0 = = 555.0/0); System.out.println (-8/a); System.out.println (0/0); }}

Output Result:

5.2345557
True
NaN
False
True
-infinity
Exception in thread "main" java.lang.ArithmeticException:/By zero
At Com.citi.icg.portal.resource.service.impl.TestDate.main (testdate.java:22)

• Java7 using underscores in new values

By using underscores to separate values, you can more visually distinguish how many bits are contained in a numeric constant.

　　　　

　　

"Crazy Java Handout" (v)----data types