If, if-else, if else-if else Statements

The if-else class of statements should have the following form:

if (condition) { statements;} if (condition) { statements;} else { statements;} if (condition) { statements;} else if (condition) { statements;} else { statements;}

Note: if statements always use braces {}. Avoid the following error-prone form:

if (condition) //AVOID! THIS OMITS THE BRACES {}! statement;

For Statements

A for statement should have the following form:

for (initialization; condition; update) { statements;}

An empty for statement (one in which all the work is done in the initialization, condition, and update clauses) should have the following form:

for (initialization; condition; update);

When using the comma operator in the initialization or update clause of a for statement, avoid the complexity of using more than three variables. If needed, use separate statements before the for loop (for the initialization clause) or at the end of the loop (for the update clause).

While Statements

A while statement should have the following form:

while (condition) { statements;}

An empty while statement should have the following form:

while (condition);

Do-while Statements

A do-while statement should have the following form:

do { statements;} while (condition);

Switch Statements

A switch statement should have the following form:

switch (condition) {case ABC: statements; /* falls through */ case DEF: statements; break; case XYZ: statements; break; default: statements; break;}

Every time a case falls through (doesn't include a break statement), add a comment where the break statement would normally be. This is shown in the preceding code example with the /* falls through */ comment.

Every switch statement should include a default case. The break in the default case is redundant, but it prevents a fall-through error if later another case is added.

Try-catch Statements

A try-catch statement should have the following format:

try { statements;} catch (ExceptionClass e) { statements;}

A try-catch statement may also be followed by finally, which executes regardless of whether or not the try block has completed successfully.

try { statements;} catch (ExceptionClass e) { statements;} finally { statements;}

White Space

Blank Lines

Blank lines improve readability by setting off sections of code that are logically related.

Two blank lines should always be used in the following circumstances:

• Between sections of a source file
• Between class and interface definitions

One blank line should always be used in the following circumstances:

• Between methods
• Between the local variables in a method and its first statement
• Before a block (see section 5.1.1) or single-line (see section 5.1.2) comment
• Between logical sections inside a method to improve readability

Blank Spaces

Blank spaces should be used in the following circumstances:

• A keyword followed by a parenthesis should be separated by a space. Example:

while (true) { ... }

Note that a blank space should not be used between a method name and its opening parenthesis. This helps to distinguish keywords from method calls.

• A blank space should appear after commas in argument lists.
• All binary operators except . should be separated from their operands by spaces. Blank spaces should never separate unary operators such as unary minus, increment ("++"), and decrement ("--") from their operands. Example:

a += c + d; a = (a + b) / (c * d); while (d++ = s++) { n++; } printSize("size is " + foo + "\n");

• The expressions in a for statement should be separated by blank spaces. Example:

for (expr1; expr2; expr3)

• Casts should be followed by a blank space. Examples:

myMethod((byte) aNum, (Object) x); myMethod((int) (cp + 5), ((int) (i + 3)) + 1);

Naming Conventions

Naming conventions make programs more understandable by making them easier to read. They can also give information about the function of the identifier-for example, whether it's a constant, package, or class-which can be helpful in understanding the code.

Identifier Type	Rules for Naming	Examples
Packages	The prefix of a unique package name is always written in all-lowercase ASCII letters and should be one of the top-level domain names, currently com, edu, gov, mil, net, org, or one of the English two-letter codes identifying countries as specified in ISO Standard 3166, 1981. Subsequent components of the package name vary according to an organization's own internal naming conventions. Such conventions might specify that certain directory name components be division, department, project, machine, or login names.	com.sun.eng com.apple.quicktime.v2 edu.cmu.cs.bovik.cheese
Classes	Class names should be nouns, in mixed case with the first letter of each internal word capitalized. Try to keep your class names simple and descriptive. Use whole words-avoid acronyms and abbreviations (unless the abbreviation is much more widely used than the long form, such as URL or HTML).	class Raster; class ImageSprite;
Interfaces	Interface names should be capitalized like class names.	interface RasterDelegate; interface Storing;
Methods	Methods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized.	run(); runFast(); getBackground();
Variables	Except for variables, all instance, class, and class constants are in mixed case with a lowercase first letter. Internal words start with capital letters. Variable names should not start with underscore _ or dollar sign $ characters, even though both are allowed. Variable names should be short yet meaningful. The choice of a variable name should be mnemonic- that is, designed to indicate to the casual observer the intent of its use. One-character variable names should be avoided except for temporary "throwaway" variables. Common names for temporary variables are i, j, k, m, and n for integers; c, d, and e for characters.	int i;char c;float myWidth;
Constants	The names of variables declared class constants and of ANSI constants should be all uppercase with words separated by underscores ("_"). (ANSI constants should be avoided, for ease of debugging.)	static final int MIN_WIDTH = 4; static final int MAX_WIDTH = 999; static final int GET_THE_CPU = 1;

Programming Practices