Google Java Style

Google Java style defines some hard-and-fast rules, no non-enforceable advices.

• Import ordering:
  1. All static import.
  2. First-party packages.
  3. Third-party packages.
  4. java imports.
  5. javax imports.
• Class member ordering: It should have some logical order, but no hard and fast rule here.
• Overloads (and constructors) should appear sequentially, with no intervening members.
• Always use braces, even when the body of a block contains only one statement.
• Egyptian brackets.
  • No line break after the brace if it is followed by a comma.
  • A few exceptions for enum classes and empty block {}.
• Some exceptions for column limit:
  • A long URL in Javadoc.
  • Command lines in a comment that may be cut-and-pasted into a shell.
  • package and import statements.
• Line wrapping:
  • Prefer to break at a higher syntactic level.
  • At least +4 spaces.
• Space rules:

@SomeAnnotation({a, b})
String[][] x = foo;
new int[] {5, 6};
for (x : collection) {}
(X) x; // Space in casting.
enum Suit { CLUBS, HEARTS, SPADES, DIAMONDS }

• Horizontal alignment: Never required.
• One variable per declaration. Declare when needed, initialized as soon as possible.

int a;
int b;

• Array initializers can be block-like:

new int[] {
  0, 1,
  2, 3,
};

• Fall-through in a switch case must be commented // fall through.
• default statement must be present, even if it contains no code.
• Modifier ordering: public protected private abstract static final transient volatile synchronized native strictfp
• long-valued literals use an uppercase L suffix, never lowercase.
• Naming rules:
  • Generally, don’t use underscores.
  • ThisIsClass
  • thisIsMethod
  • Underscores may appear in JUnit test method names: test<MethodUnderTest>_<state>
  • CONSTANT_CASE
  • nonConstantFieldNames (static or otherwise) with no ‘m’ or ‘s’ prefix.
  • XmlHttpRequest // Acronyms.
  • customerId // Id.
  • supportsIpv6OnIos // IPv6 and iOS.
  • YouTubeImporter, AdWords // YouTube and AdWords.
• You should always use @Override unless when the parent method is @Deprecated.
• Exception for empty catch block in tests (use special name expected):

try {
  emptyStack.pop();
  fail();
} catch (NoSuchElementException expected) {
}

• At-clauses ordering in Javadoc: @param, @return, @throws, @deprecated.
• When an at-clause doesn’t fit on a single line, continuation lines are indented 4+ spaces from the position of the @.
• Javadoc summary fragments are not a (imperative) sentence. They are usually just a noun phrase or verb phrase.