"Java Fundamentals" June 9

1. Java Comment: single-line comment, multiline comment, document comment

Document comments: Execute Javadoc, generate HTML-formatted code reports;

Multi-line annotations do not allow nesting.

2. Identifier naming specification

Package name: all words lowercase;

Class name Interface name: All words capitalized in the first letter;

Variable name and function name: The first word is lowercase and the first letter of each word is capitalized;

Constant name: All words capitalized, each word underlined ' _ ' connection.

Note: The keyword cannot be an identifier;

Keyword all letters lowercase.

3, negative number of binary: Take the reverse plus one

4. Data type

Basic data types: Byte, short, int (integer default), long, float, double (decimal default)

Char

Boolean

Reference data type: class, interface, []

Note: Data type conversions

 Short num = 9= num + 10;

Compile error, 10 default to int type, ' = ' data type inconsistent, need to cast

num = (short) (num + 10);

Attention:

 Short num = 9+ =  10;

The compilation was successful because it was converted automatically.

"Programing in Java" explains:

Q. is there any difference between a + = b and a = a + b, where a and b are PR Imitive types?

A. possibly, if A and b are of different types. The assignment statement A + = b is equivalent to a = (int.) (A + B) if a is of type I NT. Thus, if b is of type double, a + = b are legal, but a = a + b is a compile-time Error.

5. String connector, addition operator

Note: string data and any data are connected with ' + '

1  Public classHello2 {3      Public Static voidMain (string[] args)4     {5         intA = 4, B;6b = a++;7System.out.println ("a =" + A + ", B =" +b);8SYSTEM.OUT.PRINTLN ("AB =" + A +b);9System.out.println ("a + b =" + (A +b));Ten     } One}

6. Shift

>>: Fill the vacancy with the sign bit

>>>: with 0 fill vacancies

"Java Fundamentals" June 9