Java enum class with values1/18/2024 values ( ) for ( int i = 0 i < planetValues. parseDouble (args ) double mass = earthWeight /EARTH. Here is some code that shows you how to use the Day enum defined above:ĭay day public EnumTest (Day day ) double earthWeight = Double. That includes natural enum types such as the planets in our solar system and data sets where you know all possible values at compile time-for example, the choices on a menu, command line flags, and so on. You should use enum types any time you need to represent a fixed set of constants. For example, you would specify a days-of-the-week enum type as: In the Java programming language, you define an enum type by using the enum keyword. Common examples include compass directions (values of NORTH, SOUTH, EAST, and WEST) and the days of the week.īecause they are constants, the names of an enum type's fields are in uppercase letters. The variable must be equal to one of the values that have been predefined for it. It has been formatted to fit your course.Īn enum type is a special data type that enables for a variable to be a set of predefined constants. Suppose we have the SitePointChannel enumeration with the list of channels and we need to add to each channel the number of published articles.Note: This reading has been modified from its original version. Feels unfortunate that they did not make an 'enum with aliases' part of Java. I think some benefits of native enum are lost however, e.g. It is basically a data type that lets you. Let’s go through an example for this problem. Might even report the display-name (override toString()) by looking up until grandparent class is null. Beginners Guide to Java eNum An enum is just like any other Java Class, with a predefined set of instances. Fields and constructors (as well as methods) must be defined below the list of constants. As I mentioned earlier, each enumeration constant is an object of its enumeration type, so a constructor is called for each of the enumeration constants. In order to define values, the enclosing type must have a constructor that accepts parameters. Keep in mind that as with instances of a regular class, each enumeration constant has its own fields. Java enumeration constants can have fields, which must be given a value at creation time. For example, comparing it to SitePointChannel.JAVASCRIPT will return the value -2. If the reference enum instance is compared with instances that come after it in the enum class, it will return a negative value. It is good practice to list all enum constants (even if some of them don’t do anything) and add a default branch, usually with an exception (in case a new constant gets added and someone misses the switch statement and doesn’t update it.) The signatures of these methods are as follows (assuming the name of the enum class is EnumClass ): EnumClass.valueOf(value: String): EnumClass EnumClass. This is due to the fact the enum type is implicitly specified in the switch expression. Enum classes in Kotlin have synthetic properties and methods for listing the defined enum constants and getting an enum constant by its name. In switch statements, enumeration constants are used without their enumeration type name. Check out the official page on Java enums to see official examples, specifically the example with planets for your. In this case, you can provide a marriage field and set it in a constructor just like you would for any other object. You can give it fields, methods, and constructors. specify an enumeration constant switch (channel ) A Java enum is an object, just like other objects in most ways. Here is an example that prints the content of a given channel: SitePointChannel channel =. Another very widely used feature of enumerations is the ability to control switch statements.
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