Often asked: How To Use Enums In Java?

How do you use enum in Java?

Example of applying Enum on a switch statement

  1. class EnumExample5{
  3. public static void main(String args[]){
  4. Day day=Day.MONDAY;
  5. switch(day){
  6. case SUNDAY:
  7. System.out.println(“sunday”);
  8. break;

How do you use enums?

Enums are lists of constants. When you need a predefined list of values which do represent some kind of numeric or textual data, you should use an enum. You should always use enums when a variable (especially a method parameter) can only take one out of a small set of possible values.

How do you declare an enum?

An enum is defined using the enum keyword, directly inside a namespace, class, or structure. All the constant names can be declared inside the curly brackets and separated by a comma. The following defines an enum for the weekdays. Above, the WeekDays enum declares members in each line separated by a comma.

How do I create an enum in an enum?

We can’t instantiate an enum using the new operator. We can also provide various values as enum -member variables with the enum constants. We can create abstract methods within an enum. In that case, all of the Enum constants will become abstract and will be required to implement declared abstract methods.

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What is enum keyword in Java?

The enum keyword declares an enumerated (unchangeable) type. 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.

What is purpose of enum in Java?

The main objective of enum is to define our own data types(Enumerated Data Types). Declaration of enum in java: Enum declaration can be done outside a Class or inside a Class but not inside a Method.

Can enums have methods?

The enum class body can include methods and other fields. The compiler automatically adds some special methods when it creates an enum. For example, they have a static values method that returns an array containing all of the values of the enum in the order they are declared.

Are enums singletons?

Enum Singletons are new ways of using Enum with only one instance to implement the Singleton pattern in Java. While there has been a Singleton pattern in Java for a long time, Enum Singletons are a comparatively recent term and in use since the implementation of Enum as a keyword and function from Java 5 onwards.

Can we pass enum as parameter in Java?

An enum is a class. So you can pass an instance of the class ( EnumValues. generalInformation. PHONE for example), or you can pass the class itself ( EnumValues.

What is enum size?


Range of Element Values Enum Options
0.. 2147483647 4 bytes unsigned 4 bytes signed
0.. 4294967295 4 bytes unsigned 4 bytes unsigned
-2147483648.. 2147483647 4 bytes signed 4 bytes signed
0.. (263 -1) (C++ only) 8 bytes unsigned 8 bytes signed
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What is an enum value?

In computer programming, an enumerated type (also called enumeration, enum, or factor in the R programming language, and a categorical variable in statistics) is a data type consisting of a set of named values called elements, members, enumeral, or enumerators of the type.

Why is enum constructor private?

We need the enum constructor to be private because enums define a finite set of values (SMALL, MEDIUM, LARGE). If the constructor was public, people could potentially create more value. (for example, invalid/undeclared values such as ANYSIZE, YOURSIZE, etc.). Enum in Java contains fixed constant values.

Can two enums have the same value Java?

Two enum names can have same value. For example, in the following C program both ‘Failed’ and ‘Freezed’ have same value 0. 2. If we do not explicitly assign values to enum names, the compiler by default assigns values starting from 0.

Can we extend enum in Java?

No, we cannot extend an enum in Java. Java enums can extend java. lang. Enum class implicitly, so enum types cannot extend another class.

How do you find the value of an enum?

Java enum with string values

  1. Create java enum with string values. Java program to create enum with strings.
  2. Iterate enum constants. To iterate over enum list, use values () method on enum type which return all enum constants in an array.
  3. Java enum to String.
  4. Get enum by name – enum string parameter.
  5. Reverse Lookup – Get enum name from value.

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