Name Java Code Conventions Translator Morning Introduction This document describes the code specification of Java language, compared with Mr. Chen Shizhong's "C Code Specification", this article is a short-sighted. The terms listed in the terms, from coding style, to precautions, not only Java, for other languages, are also known for other languages. Because of a short, it is easy to book, everyone may wish to use this as a Handbook, a standing case, an eye-on. Declaration requires copying, dissemination, please attach this statement, thank you. Original source: http://java.sun.com/docs/codeconv/html/codeconvtoc.doc.html, the translation source: http://morningspace.51.net/ ,moyingzz@etang.com
table of Contents
1 Introduction
1.1 Why is there a coding specification 1.2 copyright statement
2 file name
2.1 File suffix 2.2 Common file name
3 file organization
3.1 Java source file
3.1.1 Opening Note 3.1.2 Package and Introduction Statements 3.1.3 Class and Interface Declaration
4 indentation
4.1 Row length 4.2 Renewal
5 note
5.1 Format of implementing comments
5.1.1 Member 5.1.2 Untrial Notes 5.1.3 Tail Note 5.1.4 Live Note 5.2 Word Net Notes
6 declaration
6.1 The number of declared variables per line 6.2 Initialization 6.3 Layout 6.4 and interface declaration
7 statement
7.1 Simple Statement 7.2 Composite Schedule 7.3 Return Statement 7.4 IF, IF-ELSE, IF ELSE-IF ELSE Statement 7.5 for Statement 7.6 While Statement 7.7 Do-While Statement 7.8 Switch Statement 7.9 Try-Catch Statement
8 blank
8.1 Empty Route 8.2 Space
9 naming specification
10 programming practice
10.1 Provides access control of examples and class variables 10.2 Reference class variable and class method 10.3 Constant 10.4 variable assignment 10.5 Other conventions
10.5.1 Clay 10.5.2 Return Value 10.5.3 Conditional Operator "?" The expression "?" Before the expression 10.5.4 Special notes
11 code example
11.1 Java source file example
1 Introduction
1.1 Why have the code specification (Why Have Code Conventions)
The code specification is especially important for programmers. There are several reasons: - A software cycle of software is maintenance - there is almost no software, in its entire life cycle, all of the initial developers To maintain - encoding specifications can improve software readability, allowing programmers to completely understand new code as soon as possible - if you put the source code as a product, you need to make it very well packaged and clear, one If any other products you have built In order to implement specifications, each software developers must consistently comply with the coding specification. everyone.
1.2 Copyright Notice (ACKNOWLEDGMENTS)
This document reflects the coding standard part of Sun Microsystems, Java language norms. The main contributors include: Peter King, Patrick Naughton, Mike Demoney, Jonni Kanerva, Kathy Walrath, and Scott Hommel. This document is now maintained by Scott Hommel, please send it to Shommel@eng.sun.com for comments.
2 file name (File names)
This part lists the commonly used file names and their suffixes.
2.1 File suffixes (File Suffixes)
Java program uses the following file suffix: file category file suffix java source file .javajava byte code file .class
2.2 Common file names (Common file names)
Common file names include:
The preferred file name of the file name use gnumakefilemakefiles. We use Gnumake to create a (Build) software. ReadMe Overview of the preferred file name of the file included in the specific directory
3 file organization (File ORGANIZATION)
A file is constructed by a paragraph divided by a space, and an optional annotation that identifies each paragraph. More than 2,000 rows of procedures are difficult to read and should be avoided as much as possible. "Java Source File Example" provides a reasonable Java program example.
3.1 Java Source File (Java Source Files)
Each Java source file contains a single public class or interface. If private and interfaces are associated with a public class, they can put them and public classes in the same source file. The public category must be the first class or interface in this file. The Java source file also follows the following rules:
- At the beginning of the comment (see "Opening Note") - Package and introduction statement (see "Package and Introduction Statements") - Class and Interface Declaration (see "Class and Interface Declaration")
3.1.1 BEGINNING Comments
All source files should have a C language style annotation in the beginning, where the class name, version information, date, and copyright statement: / *
* ClassName
*
* Version Information
*
* Date
*
* CopyRight Notice
* /
3.1.2 Packages and introduction statements (Package and Import Statements)
In most Java source files, the first non-promised line is a packet statement. You can follow the introduction statement after it. For example: package java.aw;
Import java.awt.peer.canvaspeer;
3.1.3 Class and Interface Declaration (Class and Interface Declarations)
The following table describes the various parts of the class and interface declarations and the order of them appear. See "Java Source File Example" An example of a comment.
Particular / Interface Declaration of Part 1 / Interface Document Note (/ ** ... * /) This annotation is included in this comment, see "Document Notes" 2 or Interface Declaration 3 / Interface Implementation (/ * ... * /) If necessary, the comment should contain any information about the entire class or interface, and this information is not suitable as a class / interface document comment. The 4 types of (static) variables are firstcoming the common variables of the class, followed by the protection variable, and then the package level variable (no access modifier, access modifier), and finally the private variable. 5 instance variables are first common, followed by the protection level, and then the package level (no access to the modifier), and finally the private level. 6 Structure 7 Methods These methods should be packet according to functions, rather than scope or access. For example, a private class method can be placed between two public instance methods. Its purpose is to make it easier to read and understand the code.
4 indentation typesetting (Indentation)
4 spaces are often used as a unit of indentation. The exact interpretation of indentation is not specified in detail (space VS. Table). A tab is equal to 8 spacers (rather than 4).
4.1 Line Length
Try to avoid a row of more than 80 characters, because many terminals and tools cannot be well processed. Note: The examples used in the document should use a shorter chance, and the length is generally not more than 70 characters.
4.2 Wrapping Lines
When an expression cannot be accommodated in one line, it can be disconnected according to the following general rules: - Disconnect behind a comma - disconnected in front of an operator - Ning better to select a higher level (Higher-Level), Not a lower level (Lower-Level) - New line should be aligned with the beginning of the same level expression - If the above rules have caused your code to confuse or make your code piled up on the right, then In order to indent the 8 spaces. The following is some examples of disconnect calls: SomeMethod (LONGEXPIPRESSION1, LONGEXPIPRESSION2, LONGEXPRESSION3, LONGEXPRESSION4, LONGEXPRESSION5);
Var = SomeMethod1 (LONGEXPRESSION1,
SomeMethod2 (LONGEXPRESSION2,
LONGEXPIESSION3)))
The following is an example of two breakdown spell expressions. The former is better because the disconnect is located outside the bracket expression, which is a higher level of disconnection. Longname1 = longname2 * (longname3 longname4 - longname5)
4 * longname6; // preffer
Longname1 = longname2 * (longname3 longname4
- longname5) 4 * longname6; // Avoid
The following is an example of two indentation methods declared. The former is a conventional situation. If the latter uses a routine indentation method, the second line and the third row are moved very rely very, so the generation is indented in 8 space // conventional Indentation.
SomeMethod (int Anarg, Object Anothererarg, String Yetanotherarg,
Object andstillanother {
...
}
// Indent 8 spaces to avoid very deep indents
Private static synchronized horkinglongmethodname (int Anarg,
Object Anotherarg, String Yetanothererarg,
Object andstillanother {
...
}
The wrap of the IF statement usually uses 8 space rules, because conventional indentation (4 spaces) will make the statement look more difficult. For example: // don't use this indentation
IF (Condition1 && Condition2)
|| (Condition3 && Condition4)
||! (Condition5 && condition6)) {// bad wraps
DOSMETHINGABOUTIT (); // make this line easy to miss
}
// use this indeetation instead
IF (Condition1 && Condition2)
|| (Condition3 && Condition4)
||! (Condition5 && condition6)) {
DOSMETHINGABOUTIT ();
}
// or us
IF (Condition1 && Condition2) || (Condition3 && Condition4)
||! (Condition5 && condition6)) {
DOSMETHINGABOUTIT ();
}
There are three feasible methods for processing three-yuan arithmetic expression: alpha = (AlongBooleaneXpression)? Beta: gamma; alpha = (AlongBooleaneXpression)? Beta
: gamma;
Alpha = (AlongBooleaneXpression)
? beta
: gamma;
5 Note (Comments)
The Java program has two types of annotations: Implementation Comments and Documents (Document Comments). Realizing comments are those who have seen in C , use /*...*/ and // definitions. Document Note (known as "DOC Comments") is a unique java and is defined by / the / **.... Document comments can be converted to an HTML file through the JavaDoc tool. Realize comments to comment code or implement detail. Document Note describes the code from the perspective of the IMPLEMentation-Free. It can be read by those developers who have no source code. Note Should be used to give a summary of the code and provide additional information provided by code itself. Note Should only include information related to the reading and understanding procedures. For example, information such as how the corresponding packet is established or in which directory should not be included in the comment. In the comment, it is possible to explain the important or not obvious place in design decisions, but it should be avoided. Excessive annotations are easy to obsolete. It is usually avoided that the code updates may be more comments. Note: Frequent comments sometimes reflect the low quality of the code. When you feel forced to add anything, consider rewriting the code clearer. Comments should not be written in the big boxes drawn in an asterisk or other character. Note Should not include special characters such as patriant characters and backfall.
5.1 Implementation Comment Formats (IMPLEMENTATION China
The programs can have four things that implement annotations: block, single-line, tail, and end-of-line.
5.1.1 Block Comments (Block Comments)
Block comments are typically used to provide descriptions for files, methods, data structures, and algorithms. Block comments are placed at the beginning of each file and before each method. They can also be used elsewhere, such as internal interior. Block note inside features and methods should have the same indentation format with the code they described. The first block of the block should have a blank line, which is used to discrolize block annotations and code, such as: / *
* Here is a block Comment.
* /
Block comments can begin with / *, so that Indenter can identify it as the beginning of a code block without rearing it. / * -
* Here Is A Block Comment with Some Very Special
* Formatting That I Want Indent (1) To ignore.
*
* One
* TWO
* Three
* /
Note: If you don't use Indent (1), you don't have to use / * -, or to run Indenter for others in your code.
See "Document Notes"
5.1.2 Single-line Comments (SINGLE-LINE Comments)
Short comments can be displayed in one line and have the same indented level with the subsequent code. If a note cannot be written within one line, it will be used (see "Block Comment"). There should be an empty line before a single line comment. The following is an example of a single-line annotation in a Java code:
IF (Condition) {
/ * Handle the condition. * /
...
}
5.1.3 Tail Note (Trailing Comments)
The extremely short comment can be located in the same row with the code they want, but there should be sufficient blank to separate the code and comments. If there is a plurality of short comments appear in large segment code, they should have the same indentation. The following is an example of the tail end annotation in a Java code: if (a == 2) {return true; / * special case * /
} else {
Return isprime (a); / * Works Only for ODD A * /
}
5.1.4 Wing Note (End-of-Line Comments)
Comment default "//", you can comment out part of the row or a line. It is generally not used for annotation text; however, it can be used to comment out of the continuous multi-line code segment. The following is an example of all three styles: if (foo> 1) {
// Do a double-flip.
...
}
Else {
Return false; // explain why here.
}
// if (bar> 1) {
//
// // do a triple-flip.
// ...
//}
// else {
// Return False;
//}
5.2 Document Notes (Documentation Comments)
Note: Examples of the annotation format described here, see "Java Source File Example"
If you want to know more, see "How to Write Doc Comments for Javadoc", which contains information about document comment tags (@Return, @param, @see):
Http://java.sun.com/javadoc/writingdoccomments/index.html
For more information about document comments and javadoc, see Javadoc's Home:
http://java.sun.com/javadoc/index.html
Document Note Description Java class, interface, constructor, method, and field (field). Each document comment will be placed in the comment delimiter / **...*/, a comment corresponds to a class, interface or member. This comment should be before the declaration:
/ **
* The Example Class Provide ...
* /
Public class example {...
Note that the top-level and interfaces are not indent, and their members are indent. The first row (/ **) describing the document annotation of the classes and interfaces does not need to be indented; the subsequent document comments are indented in each row (align the asterisk). Members, including constructor, the first line of its document comments indent 4 grids, and then indent the 5 grid per line.
If you want to give information about classes, interfaces, variables, or methods, and this information is not suitable for writing in the document, you can use the implementation block annotation (see 5.1.1) or tightly follow the separate note behind the declaration (see 5.1.2). For example, the details of a class implementation should be placed in a block annotation that keeps followed by the class declaration, not in the document comment.
Document comments cannot be placed in a definition block of a method or constructor, since Java will associate the first declaration after the document comment is associated with it.
6 Declarations
6.1 Number per line declared
Recommend a row of a statement, because it is to write a comment. That is, int discount; // Indentation Level
Int size; // size of table
To be better than, int level, size; do not place a declaration of different types of variables in the same line, for example: int foo, fooarray []; // WRONG! Note: In the above example, put it between the type and the identifier A space, another alternative way is to use tab: int level; // indeentation level
Int size; // size of table
Object CurrenTry; // Currently Selected Table Entry
6.2 Initialization
Try to initialize while declaring local variables. The only reason not to do this is that the initial value of the variable depends on some previous calculations.
6.3 Layout (Placement)
The variable is declared at the beginning of the code block. (A block refers to any code that is included in the middle of braces "{" and "}".) Do not declare when the variable is used for the first time. This will make the programs that are not concentrated, and the transplantability of the code is hindered in this scope. Void mymethod () {
INT INT1 = 0; // Beginning of Method Block
IF (Condition) {
INT INT2 = 0; // Beginning of "if" block
...
}
}
One exception to this rule is the index variable for the FOR cycle (INT i = 0; I Avoid a local variable that covers a variable of the previous declaration. For example, do not declare the same variable name in the internal code block: int count; ... mymethod () { IF (Condition) { INT count = 0; // avoid! ... } ... } 6.4 Category and Interface Declaration (Class and Interface Declarations) When writing classes and interfaces, you should follow the following format rules: - The left parentheses before the method name and its parameter list "(" Do not have spaces - left braces "{" is located at the end of the declaration statement - Right Big Bouth "} "Another line, aligned with the corresponding statement statement unless it is an empty statement,"} "should follow" {"Class Sample Extends Object { INT IVAR1; INT IVAR2; Sample (int i, int j) { Ivar1 = i; Ivar2 = j; } Int emptymethod () {} ... } - Method and method separation 7 statement (statements) 7.1 Simple STATEments Each line contains a statement, for example: Argv ; // Correct Argc -; // Correct Argv ; argc--; // avoid! 7.2 Composite Statements (Compound Statements) The composite statement is a statement sequence contained in braces, such as "{statement}". For example, the following paragraphs. - Included in which the statement should be compained in a hierarchy - left braces "{" should be located at the end of the initial line of the complex statement; the right braces "}" should be partially row and composite statement . - Brackets can be used for all statements, including a single statement, as long as these statements are part of the IF-ELSE or FOR control structure. This makes it easy to add a statement without worrying to introduce bugs due to adding parenthesis. 7.3 Return statement (Return Statements) A returnis statement with a return value does not use parentheses "()" unless they make the return value more prominent in some way. Return; Return mydisk.size (); RETURN (SIZE? SIZE: DEFAULTSIZE); 7.4 IF, IF-ELSE, IF ELSE-IF ELSE statement (IF, IF-ELSE, IF ELSE-IF ELSE STATEMENTS) The IF-ELSE statement should have the following format: if (condition) { STATEMENTS; } IF (Condition) { STATEMENTS; } else { STATEMENTS; } IF (Condition) { STATEMENTS; } else if (condition) { STATEMENTS; } else { STATEMENTS; } Note: The IF statement is always enclosed in "{" and "}" to avoid the use of the following format: if (condition) // avoid! This OMITS the bracs {}! STATEMENT; 7.5 for statement (for Statements) A FOR statement should have the following format: for (Initialization; Condition; Update) { STATEMENTS; } An empty FOR statement (all work is completed in initialization, conditional judgment, update clause) should have the following format: for (Initialization; Condition; Update); When using a comma in the initialization of the for statement or in the update clause, avoiding the use of three variables, resulting in complexity. If necessary, use a separate statement before the FOR cycle (for the initialization subsis) or the FOR cycle (for the update clause). 7.6 While Statement (While Statements) A While statement should have the following format while (condition) { STATEMENTS; } A empty While statement should have the following format: while (condition); 7.7 Do-While Statement (Do-While Statements) A Do-While statement should have the following format: do { STATEMENTS; WHILE (condition); 7.8 Switch statement (Switch Statements) A Switch statement should have the following format: switch (condition) { Case ABC: STATEMENTS; / * Falls through * / Case Def: STATEMENTS; Break; Case XYZ: STATEMENTS; Break; DEFAULT: STATEMENTS; Break; } Whenever a CASE is executed down (because there is no BREAK statement), you should usually add a comment at the location of the BREAK statement. In the sample code above, comments / * falls through * /. 7.9 try-catch statement (Try-catch statements) A try-catch statement should have the following format: try { STATEMENTS; } catch (exceptionclass e) { STATEMENTS; } Behind a try-catch statement is also followed by a Finally statement, regardless of whether the TRY code block is successfully implemented, it will be executed. Try { STATEMENTS; } catch (exceptionclass e) { STATEMENTS; } finally { STATEMENTS; } 8 blank (White Space) 8.1 Blank Lines The rule is separated from the logical code segment to improve readability. The following conditions should always use two space lines: - a segment between a source file - class declarations and interface declarations should always use an empty line: - Between the two methods - the first statement of local variables and methods within the method - block annotation (see "5.1.1") or a single-line annotation (see "5.1.2") - one method Between logic segments to improve readability 8.2 spaces (Blank Spaces) The following conditions should be used in space: - a keyword that keeps with parentheses should be separated by spaces, for example: while { ... } Note: The space should not be placed between the method name and the left brackets. This will help distinguish between keywords and method calls. - Blank should be in the back of the comma in the parameter list - all binary operators, except ".", You should use spaces to separate from the operand. The one-dollar operator and the operand is not due to the splitter, such as: negative (" ") and self-reduction ("-"). For example: A = C D; A = (a b) / (c * d); While (D = s ) { N ; } PRINTSIZE ("Size IS" FOO "/ N"); - The expression in the for statement should be separated by spaces, for example: for (expr1; expr2; expr3) - It should be followed by a space after compulsory transformation, for example: MyMethod ((Byte) Anum, (Object) x); MyMethod ((int) (CP 5) ((int) (I 3)) 1); 9 Name Specification (Naming Conventions) Naming specification makes the program more readily, making it easier to understand. They can also provide information about identifier functions to help understand code, for example, whether it is a constant, package, or class. Identifier Type Name Rules Example Pack (Packages) A unique package prefix is always lower-write ASCII letters and is a top domain name, usually COM, EDU, GOV, MIL, NET, ORG, or 1981 ISO 3166 Standard Specified English Double Character Code in the country. The subsequent part of the package is not the same as the naming specification within the respective mechanisms. Such naming specifications may distinguish between departments, projects, or registration names in a specific directory name. com.sun.engcom.apple.quicktime.v2edu.cmu.cs.bovik.chese class (Classes) Names Rules: Classified is a word, using case-by-case mixing, the first letter of each word. Try to make your class name simple and description. Use intact words to avoid abbreviations (unless the abbreviation words are more widely used, like url, html) class rasser; Class ImageSprite; interface (interfaces) Naming rules: case-sensitive rules are similar to Interface RasterDelegate; interface storing; method Methods) method name is a verb, which uses cases of cases mixed, and the first letter of the first word is lowercase, the first letter of the words. Run (); Runfast (); getBackground (); variable (variables) In addition to the variable name, all instances, including classes, types, usual, using case-write mix, the first letter of the first letter, after the word The initial letters. The variable name should not begin with the scribe or dollar symbol, although this is allowed in grammar. The variable name should be short and described. The selection of the variable name should be easy to remember, that is, it can be pointed out. Try to avoid a variable name of a single character unless it is a disposable temporary variable. Temporary variables are usually named I, J, K, M and N, which are generally used for integer; C, D, E, which are generally used for characters. CHAR C; INT i; FLOAT MYWIDTH; instance variable (instance variables) case, in addition to the number of variable names, in addition to a downline int _employeid; string _name; Customer _CUSTOMER; constant (constants), a statement, and ANSI constants, should All uppercase, interlaced interlaced in words. (Try to avoid ANSI constants, easy to cause errors) Static final int min_width = 4; static final int max_width = 999; static final int GET_THE_CPU = 1; 10 Programming Formula (Programming Practices) 10.1 Provides access control for examples and class variables (Providing Access To Instance and Class Variables) If there is not enough reason, don't declare an instance or class variable as public. Typically, instance variables do not require explicit settings (SET) and gotten, which is usually produced as the edge effect of method calls (Side Effect). A proper example of a public instance variable is that the class is only the data structure, no behavior. That is, if you want to use a structure rather than a class (if the Java supports the structure), then the instance variable declaration of the class is suitable. 10.2 Reference Class Variables and Class Methods (Referring to Class Variables and Methods) Avoid access to a class of static variables and methods with an object. You should be replaced by a class name. For example: classMethod (); //okaclass.classmethod (); // ok Anobject.classMethod (); // avoid! 10.3 Constants In addition to the digital constant of the counter value in the FOR cycle, in addition to -1, 0 and 1, it should not be written directly to code. 10.4 variable assignment (variable assignments) Avoid value to multiple variables in one statement. It is hard to read. For example: foobar.fchar = barfoo.lchar = 'c'; // Avoid! Do not use the assignment operator to be confused with the equivalent relationship operator. For example: IF (C = D ) {// Avoid! (Java Disallows) ... } It should be written into IF ((C = D )! = 0) { ... } Do not use embedded assignment operators to try to improve the efficiency of runtime, which is the work of the compiler. For example: d = (a = b c) r; // avoid! It should be written as a = B C; D = a r; 10.5 Other Practices (Miscellaneous Practices) 10.5.1 Parentheses (PARENTHESES) In general, the use of parentheses in an expression containing a variety of operators to avoid operator priority issues, it is a good way. Even if the priority of the operator may be clear, it is not necessary for others. You can't assume that other programmers are as clear as you know the priority of the operator. IF (a == b && c == d) // Avoid! IF ((a == b) && (c == d)) // Right 10.5.2 Return Values Try to make your program structure in accordance with the purpose. For example: if (booleaneXpression) { Return True; } else { Return False; } It should be in this way as follows: Return BooleaneXpression; Similarly: IF (condition) { Return X; } Return Y; Should be written: return (condition? X: y); 10.5.3 Conditional Operators "?" Expressions Before '?' In The Conditional Operator If an expression containing a binary operator appears in the ternary operator "?:", Then a pair of parentheses should be added to the expression. For example: (x> = 0)? X: -x; 10.5.4 Special Comments Using XXX in the comment to identify some of the content that does not implement (BOGUS) but works. Use fixme to identify some fake and error content. 11 Code Examples (CODE EXAMPLES) 11.1 Java Source File Example (Java Source File Example) The following example shows how to reasonably layout a Java source program containing a single public class. The layout of the interface is similar. See "Class and Interface Declaration" and "Text Refidence". / * * @ (#) Blah.java 1.82 99/03/18 * * CopyRight (C) 1994-1999 Sun Microsystems, Inc. * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A. * All Rights Reserved. * * This Software Is The Confidential and ProPrietary Information of Sun * Microsystems, Inc. ("Confidential Information"). You Shall NOT * Disclose Such Confidential Information and Shall Use it Only in * Accordance with the Terms of the license agreement you entered Into * with sun. * / Package java.blah; Import java.blah.blahdy.blahblah; / ** * Class Description Goes Here. * * @version 1.82 18 Mar 1999 * @Author firstname lastname * / Public class blah extends someclass { / * A class implementation common can go here. * / / ** Classvar1 Documentation Comment * / Public static int classvar1; / ** * Classvar2 Documentation Comment That Happens To BE * More Than One Line Long * / Private static object classvar2; / ** Instancevar1 Documentation Comment * / Public Object Instancevar1; / ** Instancevar2 Documentation Comment * / Protected int instancevar2; / ** Instancevar3 Documentation Comment * / Private object [] instancevar3; / ** * ... Constructor Blah Documentation Comment ... * / Public blah () { // ... Implementation Goes Here ... } / ** * ... Method Dosomething Documentation Comment ... * / Public void dosomething () { // ... Implementation Goes Here ... } / ** * ... Method Dosomethingelse Documentation Comment ... * @Param SomeParam Description * / Public void Dosomethingelse (Object SomeParam) { // ... Implementation Goes Here ... } }
