Java enum get all constants

This is the common base class of all Java language enumeration types. More information about enums, including descriptions of the implicitly declared methods synthesized by the compiler, can be found in section 8.9 of The Java™ Language Specification . Note that when using an enumeration type as the type of a set or as the type of the keys in a map, specialized and efficient set and map implementations are available.

Constructor Summary

Method Summary

Returns the ordinal of this enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero).

Methods declared in class java.lang.Object

Constructor Detail

Enum

Sole constructor. Programmers cannot invoke this constructor. It is for use by code emitted by the compiler in response to enum type declarations.

Method Detail

name

Returns the name of this enum constant, exactly as declared in its enum declaration. Most programmers should use the toString() method in preference to this one, as the toString method may return a more user-friendly name. This method is designed primarily for use in specialized situations where correctness depends on getting the exact name, which will not vary from release to release.

ordinal

Returns the ordinal of this enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero). Most programmers will have no use for this method. It is designed for use by sophisticated enum-based data structures, such as EnumSet and EnumMap .

toString

Returns the name of this enum constant, as contained in the declaration. This method may be overridden, though it typically isn’t necessary or desirable. An enum type should override this method when a more «programmer-friendly» string form exists.

equals

hashCode

public final int hashCode()

clone

protected final Object clone() throws CloneNotSupportedException

Throws CloneNotSupportedException. This guarantees that enums are never cloned, which is necessary to preserve their «singleton» status.

compareTo

Compares this enum with the specified object for order. Returns a negative integer, zero, or a positive integer as this object is less than, equal to, or greater than the specified object. Enum constants are only comparable to other enum constants of the same enum type. The natural order implemented by this method is the order in which the constants are declared.

getDeclaringClass

Returns the Class object corresponding to this enum constant’s enum type. Two enum constants e1 and e2 are of the same enum type if and only if e1.getDeclaringClass() == e2.getDeclaringClass(). (The value returned by this method may differ from the one returned by the Object.getClass() method for enum constants with constant-specific class bodies.)

valueOf

public static Enum> T valueOf(Class enumType, String name)

Returns the enum constant of the specified enum type with the specified name. The name must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.) Note that for a particular enum type T , the implicitly declared public static T valueOf(String) method on that enum may be used instead of this method to map from a name to the corresponding enum constant. All the constants of an enum type can be obtained by calling the implicit public static T[] values() method of that type.

finalize

protected final void finalize()

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Java Enums

An enum is a special «class» that represents a group of constants (unchangeable variables, like final variables).

To create an enum , use the enum keyword (instead of class or interface), and separate the constants with a comma. Note that they should be in uppercase letters:

Example

You can access enum constants with the dot syntax:

Enum is short for «enumerations», which means «specifically listed».

Enum inside a Class

You can also have an enum inside a class:

Example

public class Main < enum Level < LOW, MEDIUM, HIGH >public static void main(String[] args) < Level myVar = Level.MEDIUM; System.out.println(myVar); >>

Enum in a Switch Statement

Enums are often used in switch statements to check for corresponding values:

Example

enum Level < LOW, MEDIUM, HIGH >public class Main < public static void main(String[] args) < Level myVar = Level.MEDIUM; switch(myVar) < case LOW: System.out.println("Low level"); break; case MEDIUM: System.out.println("Medium level"); break; case HIGH: System.out.println("High level"); break; >> >

Loop Through an Enum

The enum type has a values() method, which returns an array of all enum constants. This method is useful when you want to loop through the constants of an enum:

Example

for (Level myVar : Level.values())

Difference between Enums and Classes

An enum can, just like a class , have attributes and methods. The only difference is that enum constants are public , static and final (unchangeable — cannot be overridden).

An enum cannot be used to create objects, and it cannot extend other classes (but it can implement interfaces).

Why And When To Use Enums?

Use enums when you have values that you know aren’t going to change, like month days, days, colors, deck of cards, etc.

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Java enum get all constants

Java Enum with Strings