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Naming Conventions


Package names

  • Package names should be all lower case without underscores or other special characters.
  • Package names begin with the reversed authority part of the web address of the company of the developer. This part can be followed a by project/program structure dependent package substructure.
  • Don’t use plural form. Follow the convention of the standard API which uses for instance java.lang.annotation and not java.lang.annotations.
  • Examples: com.yourcompany.widget.button, com.yourcompany.core.api

Class, Interface and Enum Names

  • Class and enum names should typically be nouns.
  • Interface names should typically be nouns or adjectives ending with …able.
  • Use mixed case with the first letter in each word in upper case (i.e. CamelCase).
  • Match the regular expression ^[A-Z][a-zA-Z0-9]*$.
  • Use whole words and avoid using abbreviations unless the abbreviation is more widely used than the long form.
  • Format an abbreviation as a word if the it is part of a longer class name.
  • Examples: ArrayList, BigInteger, ArrayIndexOutOfBoundsException, Iterable.

Method Names

Method names should typically be verbs or other descriptions of actions

  • They should match the regular expression ^[a-z][a-zA-Z0-9]*$.
  • Use mixed case with the first letter in lower case.
  • Examples: toString, hashCode


Variable names should be in mixed case with the first letter in lower case

  • Match the regular expression ^[a-z][a-zA-Z0-9]*$
  • Further recommendation: Variables
  • Examples: elements, currentIndex

Type Variables

For simple cases where there are few type variables involved use a single upper case letter.

  • Match the regular expression ^[A-Z][0-9]?$
  • If one letter is more descriptive than another (such as K and V for keys and values in maps or R for a function return type) use that, otherwise use T.
  • For complex cases where single letter type variables become confusing, use longer names written in all capital letters and use underscore (_) to separate words.
  • Examples: T, V, SRC_VERTEX


Constants (static final fields whose content is immutable, by language rules or by convention) should be named with all capital letters and underscore (_) to separate words.

  • Match the regular expression ^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$

Other guidelines on naming

  • Avoid hiding/shadowing methods, variables and type variables in outer scopes.
  • Let the verbosity of the name correlate to the size of the scope. (For instance, use descriptive names for fields of large classes and brief names for local short-lived variables.)
  • When naming public static members, let the identifier be self descriptive if you believe they will be statically imported.
  • Further reading: Naming Section (in the official Java Style Guide)

Source: Java Style Guidelines from Oracle