This example demonstrate how to user enum‘s name() method to get enum constant name exactly as declared in the enum declaration.

package org.kodejava.basic;

enum ProcessStatus {
    IDLE, RUNNING, FAILED, DONE;

    @Override
    public String toString() {
        return "Process Status: " + this.name();
    }
}

public class EnumNameDemo {
    public static void main(String[] args) {
        for (ProcessStatus processStatus : ProcessStatus.values()) {
            // Gets the name of this enum constant, exactly as
            // declared in its enum declaration.
            System.out.println(processStatus.name());

            // Here we call to our implementation of the toString
            // method to get a more friendly message of the
            // enum constant name.
            System.out.println(processStatus);
        }
    }
}

Our program result:

IDLE
Process Status: IDLE
RUNNING
Process Status: RUNNING
FAILED
Process Status: FAILED
DONE
Process Status: DONE

This example demonstrate the use of enum ordinal() method to get the ordinal value of an enum constant.

package org.kodejava.basic;

enum Color {
    RED, GREEN, BLUE
}

public class EnumOrdinal {
    public static void main(String[] args) {
        // Gets the ordinal of this enumeration constant (its
        // position in its enum declaration, where the initial 
        // constant is assigned an ordinal of zero)
        System.out.println("Color.RED  : " + Color.RED.ordinal());
        System.out.println("Color.GREEN: " + Color.GREEN.ordinal());
        System.out.println("Color.BLUE : " + Color.BLUE.ordinal());
    }
}

The program print the following result:

Color.RED  : 0
Color.GREEN: 1
Color.BLUE : 2

As we know that Java enumeration type is powerful compared to enum implementation in other programming language. Basically enum is class typed, so it can have constructors, methods and fields.

In the example below you’ll see how a field is defined in an enumeration type. Because each constant value for the Fruit enum is a type of Fruit itself it will have its own price field. The price field holds a unique value for each constant such as APPLE, ORANGE, etc.

In the result you’ll see that the constructor will be called for each constant value and initialize it with the value passed to the constructor.

package org.kodejava.basic;

enum Fruit {
    APPLE(1.5f), ORANGE(2), MANGO(3.5f), GRAPE(5);

    private final float price;

    Fruit(float price) {
        System.out.println("Name: " + this.name() + " initialized.");
        this.price = price;
    }

    public float getPrice() {
        return this.price;
    }
}

public class EnumFieldDemo {
    public static void main(String[] args) {
        // Get the name and price of all enum constant value.
        for (Fruit fruit : Fruit.values()) {
            System.out.printf("Fruit = %s; Price = %5.2f%n",
                    fruit.name(), fruit.getPrice());
        }
    }
}

Our demo result is below:

Name: APPLE initialized.
Name: ORANGE initialized.
Name: MANGO initialized.
Name: GRAPE initialized.
Fruit = APPLE; Price =  1.50
Fruit = ORANGE; Price =  2.00
Fruit = MANGO; Price =  3.50
Fruit = GRAPE; Price =  5.00

The valueOf() method of an enum type allows you to get an enum constant that the value corresponds to the specified string. Exception will be thrown when we pass a string that not available in the enum.

package org.kodejava.basic;

public enum Day {
    SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}

package org.kodejava.basic;

public class EnumValueOfTest {
    public static void main(String[] args) {
        // Using valueOf() method we can get an enum constant whose
        // value corresponds to the string passed as the parameter.
        Day day = Day.valueOf("SATURDAY");
        System.out.println("Day = " + day);
        day = Day.valueOf("WEDNESDAY");
        System.out.println("Day = " + day);

        try {
            // The following line will produce an exception because the
            // enum type does not contain a constant named JANUARY.
            day = Day.valueOf("JANUARY");
            System.out.println("Day = " + day);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        }
    }
}

The output of the code snippet above:

Day = SATURDAY
Day = WEDNESDAY
java.lang.IllegalArgumentException: No enum constant org.kodejava.basic.Day.JANUARY
    at java.base/java.lang.Enum.valueOf(Enum.java:273)
    at org.kodejava.basic.Day.valueOf(Day.java:3)
    at org.kodejava.basic.EnumValueOfTest.main(EnumValueOfTest.java:15)