Java program accesses all constants defined in an enumeration

After JDK version 5, Java introduced enumerations. It is a set of constants defined using the keyword 'enum'. In Java, final variables are somewhat similar to enumerations.

In this article, we will create a Java program in which we define an enumeration class and try to access all the constants defined in the enumeration using the valueOf() and values() methods.

The Chinese translation of

Enum

is:

Enumeration

When we need to define a fixed set of constants, we use enumeration classes. For example, if we want to use the days of the week, the names of the planets, the names of the five vowels, etc. Note that the names of all constants are declared in uppercase letters.

Although in Java, enumeration is a class type, we cannot instantiate it. Each constant defined in an enumeration is an instance of its enumeration type. It provides other features similar to a class like we can create its instance variables, methods and constructors.

grammar

Enum enumeration_name {
   // constants values
}

The Chinese translation of

Example

is:

Example

enum Planet {
   EARTH, MARS, JUPYTER, NEPTUNE, SATURN, URANUS, VENUS;
} 

The above example illustrates how we create an enumeration class. The name of the enumeration is Planet, and the variables EARTH and MARS are its constants. By default, they are declared public and static. These constants are self-typed because their type is defined by the enumeration in which they are found. In this case, their type is Planet.

Program to access all constants defined in the enumeration

valueOf() and values() are two predefined methods that will help us get the value of the constant defined in the list.

valueOf() − It returns the value of the constant passed as argument.

values() − It returns an array containing all constants in the enumeration class.

Example 1

is translated as:

Example 1

The following example demonstrates how to use the valueOf() method to obtain a constant &minuns;

enum Vibgyor { 
   // creating enumeration
   VIOLET, INDIGO, BLUE, GREEN, YELLOW, ORANGE, RED; 
   // constants
}
public class Main {
   public static void main(String[] args) {
      System.out.println("The color present in VIBGYOR: ");
      Vibgyor color = Vibgyor.ORANGE; 
      System.out.println(color + " is present at index: " + color.ordinal());
      Vibgyor colr = Vibgyor.valueOf("INDIGO"); 
      System.out.println(colr);
      System.out.print(Vibgyor.valueOf("RED"));
   }
}

Output

The color present in VIBGYOR: 
ORANGE is present at index: 5
INDIGO
RED

In the above program, we created an enumeration type named 'Vibgyor' and defined some constants. The variables 'color' and 'colr' are enumeration variables of type Vibgyor. We use these variables to get constants. Use the valueOf() method to obtain the enumeration items one by one. The ordinal() method is used to access the index value of ORANGE. Index starts from 0. We can also access constants without creating any variables.

The Chinese translation of

Example 2

is:

Example 2

The following example demonstrates how to use the values() method to obtain a constant:

enum Vibgyor {
   VIOLET, INDIGO, BLUE, GREEN, YELLOW, ORANGE, RED;
}
public class Main {
   public static void main(String[] args) {
      System.out.println("The color present in VIBGYOR: ");
      // for each loop to iterate through all constants
      for(Vibgyor color : Vibgyor.values()) {
         System.out.println(color);
      }
   }
}

Output

The color present in VIBGYOR: 
VIOLET
INDIGO
BLUE
GREEN
YELLOW
ORANGE
RED

In the above program, we have accessed all the constants with a single for each loop. values() method can access multiple values ​​at a time.

in conclusion

In this article, we discussed enum and its methods. We have created a Java program to understand how to access all the constants defined in an enum using values() and valueOf() methods.

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