Groovy Interview Questions and Answers for 5 years experience

1. What are the key differences between Groovy and Java?

   • Answer: Groovy is a dynamic language built on the JVM, offering features like dynamic typing, closures, and concise syntax, unlike Java's static typing and more verbose nature. Groovy integrates seamlessly with Java libraries and can be used for scripting, web development, and building applications. Key differences include: Dynamic vs. Static Typing, Concise Syntax vs. Verbose Syntax, built-in support for closures and metaprogramming, optional semicolons, and different approaches to object-oriented programming (e.g., Groovy's more flexible use of properties).

2. Explain Groovy closures. Provide an example.

   • Answer: Groovy closures are anonymous, inner functions that can be passed as arguments to other functions or assigned to variables. They are powerful for expressing code blocks concisely. Example: ```groovy def numbers = [1, 2, 3, 4, 5] def doubled = numbers.collect { it * 2 } println doubled // Output: [2, 4, 6, 8, 10] ``` Here, `{ it * 2 }` is a closure that doubles each element.

3. How does Groovy handle null values?

   • Answer: Groovy provides the `?.` (safe navigation operator) to avoid `NullPointerExceptions`. If an object is null, the expression short-circuits, returning null instead of throwing an exception. It also offers the `Elvis operator` (`?:`) for providing default values. Example: `person?.name ?: "Unknown"`. Groovy's `String` type also handles nulls gracefully in string concatenation.

4. What are Groovy's built-in operators? Give examples for at least three.

   • Answer: Groovy offers a range of operators beyond Java's standard set. Examples include: * **Range Operator (`..`):** Creates a range of values. `1..5` creates a range from 1 to 5 (inclusive). * **Safe Navigation Operator (`?.`):** As discussed above, prevents `NullPointerExceptions`. * **Elvis Operator (`?:`):** Provides a default value if the expression before it is null. * **Spread Operator (`*`):** Used to expand arrays or lists. * **Power Operator (`**`):** Exponentiation.

5. Describe Groovy's metaprogramming capabilities.

   • Answer: Groovy allows runtime modification of classes and objects. This is done through features like `ExpandoMetaClass` (which lets you add methods to existing classes at runtime) and the ability to override methods dynamically. This enables powerful features like dynamic scripting and extending existing libraries without modifying their source code.

6. How do you handle exceptions in Groovy?

   • Answer: Exception handling in Groovy uses the same `try-catch` block structure as Java. However, Groovy's concise syntax can make exception handling more readable. Groovy also allows for using closures within `try-catch` blocks for more compact code.

7. Explain the use of Groovy's `each` method.

   • Answer: The `each` method is used to iterate over collections (lists, maps, etc.). It's a more concise way to loop through elements compared to traditional `for` loops. Example: `myList.each { println it }`

8. What is the purpose of the `getProperty()` and `setProperty()` methods in Groovy?

   • Answer: These methods provide dynamic access to an object's properties. They are used to get and set values for properties that might not be explicitly defined in the class.

9. How can you use Groovy for scripting tasks? Give an example.

   • Answer: Groovy's dynamic nature and ease of use make it ideal for scripting. You can easily execute shell commands, manipulate files, and interact with other systems. Example: `def result = "ls -l".execute().text`

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