Java Language
- Getting started with Java Language
- Top 10 Java Errors with Solutions
- Awesome Book
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- Enum starting with number
- Enums
- Declaring and using a basic enum
- Compare and Contains for Enum values
- Convert enum to String
- Documenting enums
- Enum as a bounded type parameter
- Enum constant specific body
- Enum Polymorphism Pattern
- Enum with properties (fields)
- Enums with Abstract Methods
- Enums with constructors
- Enums with static fields
- Get enum constant by name
- Getting the values of an enum
- Implement Singleton pattern with a single-element enum
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- Zero instance enum
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Java Language Enums
Introduction
Java enums (declared using the
enum keyword) are shorthand syntax for sizable quantities of constants of a single class.
Syntax
- [public/protected/private] enum Enum_name { // Declare a new enum.
- ENUM_CONSTANT_1[, ENUM_CONSTANT_2...]; // Declare the enum constants. This must be the first line inside of the enum, and should be separated by commas, with a semicolon at the end.
- ENUM_CONSTANT_1(param)[, ENUM_CONSTANT_2(param)...]; // Declare enum constants with parameters. The parameter types must match the constructor.
- ENUM_CONSTANT_1 {...}[, ENUM_CONSTANT_2 {...}...]; // Declare enum constants with overridden methods. This must be done if the enum contains abstract methods; all such methods must be implemented.
- ENUM_CONSTANT.name() // Returns a String with the name of the enum constant.
- ENUM_CONSTANT.ordinal() // Returns the ordinal of this enumeration constant, its position in its enum declaration, where the initial constant is assigned an ordinal of zero.
- Enum_name.values() // Returns a new array (of type Enum_name[]) containing every constant of that enum everytime it is called.
- Enum_name.valueOf("ENUM_CONSTANT") // The inverse of ENUM_CONSTANT.name() -- returns the enum constant with the given name.
- Enum.valueOf(Enum_name.class, "ENUM_CONSTANT") // A synonym of the previous one: The inverse of ENUM_CONSTANT.name() -- returns the enum constant with the given name.
Remarks
Restrictions
Enums always extend java.lang.Enum, so it is impossible for an enum to extend a class. However, they can implement many interfaces.
Tips & Tricks
Because of their specialized representation, there are more efficient maps and sets that can be used with enums as their keys. These will often run quicker than their non-specialized counterparts.
Enums Related Examples
- Declaring and using a basic enum
- Compare and Contains for Enum values
- Convert enum to String
- Documenting enums
- Enum as a bounded type parameter
- Enum constant specific body
- Enum Polymorphism Pattern
- Enum with properties (fields)
- Enums with Abstract Methods
- Enums with constructors
- Enums with static fields
- Get enum constant by name
- Getting the values of an enum
- Implement Singleton pattern with a single-element enum
- Implements Interface
- Using methods and static blocks
- Zero instance enum
