Enum Java Interview Questions and Answers for 10 years experience

1. What is an enum in Java?

   • Answer: An enum (short for enumeration) is a special data type that allows you to define a set of named constants. It's a way to represent a fixed set of values, making your code more readable, maintainable, and less prone to errors compared to using integer constants or strings.

2. How do you declare an enum in Java?

   • Answer: You declare an enum using the `enum` keyword, followed by the enum's name and a list of its constants enclosed in curly braces. For example: `public enum DayOfWeek { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY }`

3. What are the benefits of using enums over integer constants?

   • Answer: Enums offer improved type safety (preventing accidental assignment of incorrect values), better readability (constants have meaningful names), and easier maintenance (no need to manage integer codes and their corresponding meanings).

4. Can you add methods to an enum?

   • Answer: Yes, you can add methods to an enum. These methods can perform actions related to the enum constants or provide additional information about them.

5. Explain the use of the `values()` method in enums.

   • Answer: The `values()` method is a static method automatically generated for every enum. It returns an array containing all the enum constants in the order they are declared.

6. How do you iterate through the constants of an enum?

   • Answer: You can use a for-each loop to iterate through the array returned by the `values()` method.

7. Can an enum implement an interface?

   • Answer: Yes, an enum can implement one or more interfaces.

8. Can an enum extend a class?

   • Answer: No, an enum cannot extend a class, but it can implicitly extend `java.lang.Enum`.

9. What is the `ordinal()` method in an enum?

   • Answer: The `ordinal()` method returns the integer position of the enum constant within the declaration order (starting from 0).

10. How do you use enums in switch statements?

    • Answer: Enums work seamlessly with switch statements, providing a cleaner and safer alternative to using integer constants.

11. Describe the use of enums in representing states or modes in a program.

    • Answer: Enums are ideal for representing states or modes because they provide a clear and type-safe way to manage a limited set of possibilities.

12. How can you define an enum with constructor and fields?

    • Answer: You can define a constructor and fields within the enum declaration, providing each constant with specific attributes.

13. Explain the concept of enum serialization in Java.

    • Answer: Enums are automatically serializable; their serialized representation includes only the name of the constant.

14. How can you compare two enum constants for equality?

    • Answer: You can use the `==` operator to compare enum constants for equality, which compares their references.

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