Java - Keywords
Keywords are reserved words which can not be used as variable names, function names, or any other identifiers. Java has a number of keywords that are available for use in programming. A list of these keywords with brief description are mentioned below. For more details about any keyword, please visit its page.
Java Keywords
| Keyword | Description |
|---|---|
| abstract | A non-access modifier. Used for classes and methods: An abstract class cannot be used to create objects (to access it, it must be inherited from another class). An abstract method can only be used in an abstract class, and it does not have a body. The body is provided by the subclass (inherited from) |
| assert | For debugging |
| boolean | A data type that can only store true and false values |
| break | Breaks out of a loop or a switch block |
| byte | A data type that can store whole numbers from -128 and 127 |
| case | Marks a block of code in switch statements |
| catch | Catches exceptions generated by try statements |
| char | A data type that is used to store a single character |
| class | Defines a class |
| continue | Continues to the next iteration of a loop |
| const | Defines a constant. Not in use - use final instead |
| default | Specifies the default block of code in a switch statement |
| do | Used together with while to create a do-while loop |
| double | A data type that can store whole numbers from 1.7e−308 to 1.7e+308 |
| else | Used in conditional statements |
| else if | Used in conditional statements |
| enum | Declares an enumerated (unchangeable) type |
| exports | Exports a package with a module. |
| extends | Extends a class (indicates that a class is inherited from another class) |
| final | A non-access modifier used for classes, attributes and methods, which makes them non-changeable (impossible to inherit or override) |
| finally | Used with exceptions, a block of code that will be executed no matter if there is an exception or not |
| float | A data type that can store whole numbers from 1.40239846 x 10-45 to 3.40282347 x 1038. |
| for | Create a for loop |
| if | Makes a conditional statement |
| implements | Implements an interface |
| import | Used to import a package, class or interface |
| instanceof | Checks whether an object is an instance of a specific class or an interface |
| int | A data type that can store whole numbers from -231 to 231-1. |
| interface | Used to declare a special type of class that only contains abstract methods |
| long | A data type that can store whole numbers from -263 to 263-1. |
| module | Declares a module. New in Java 9 |
| native | Specifies that a method is not implemented in the same Java source file (but in another language) |
| new | Creates an instance of the class. |
| package | Declares a package |
| private | An access modifier used for attributes, methods and constructors, making them only accessible within the declared class |
| protected | An access modifier used for attributes, methods and constructors, making them accessible in the same package and subclasses |
| public | An access modifier used for classes, attributes, methods and constructors, making them accessible by any other class |
| requires | Specifies required libraries inside a module. New in Java 9 |
| return | Finished the execution of a method, and can be used to return a value from a method |
| short | A data type that can store whole numbers from -32,768 to 32,767 (inclusive). |
| static | A non-access modifier used for methods and attributes. Static methods/attributes can be accessed without creating an object of a class |
| strictfp | Restrict the precision and rounding of floating point calculations |
| super | Refers to superclass (parent) objects |
| switch | Selects one of many code blocks to be executed |
| synchronized | A non-access modifier, which specifies that methods can only be accessed by one thread at a time |
| this | Refers to the current object in a method or constructor |
| throw | Creates a custom error |
| throws | Indicates what exceptions may be thrown by a method |
| transient | A non-accesss modifier, which specifies that an attribute is not part of an objects persistent state |
| try | Used to test a block of statements for error. |
| var | Declares a variable. New in Java 10 |
| void | Specifies that a method should not have a return value |
| volatile | Indicates that an attribute is not cached thread-locally, and is always read from the "main memory" |
| while | Used to create a while loop. |
Note: true, false, and null are not keywords, but they are literals and reserved words that cannot be used as identifiers.
