What You'll Learn

• Understand the key features and improvements in Java 8 to 10.
• Explain core Java concepts with clarity and confidence.
• Analyze scenario-based questions to provide effective solutions.
• Evaluate different approaches to solving practical Java problems.
• Apply Java 8 to 10 features in real-world coding scenarios.
• Identify common pitfalls in Java programming and how to avoid them.
• Solve technical problems using Java's functional programming features.
• Answer interview-style questions with precision and depth.
• Compare Java 8 to 10 features and their applications.
• Demonstrate proficiency in Java streams and lambda expressions.
• Discuss the importance of modularity introduced in Java 9.
• Prepare for interviews with mock questions and expert feedback.

Java 8 – Lambda Expressions

• What is a lambda expression in Java 8 and how does it differ from an anonymous inner class?
• Explain what 'effectively final' means in the context of lambda expressions in Java.
• What are the benefits of using lambda expressions in Java 8 for functional programming?
• What restrictions apply to the use of lambda expressions concerning variable scope and access?
• How do you define a functional interface in Java, and why is it important for lambda expressions?
• Compare and contrast the use of lambda expressions and method references in Java 8.
• How can you handle exceptions in lambda expressions in Java 8?
• How do lambda expressions in Java 8 improve performance, especially when used with the Stream API?
• What role does the '@FunctionalInterface' annotation play in Java 8, and how does this impact lambda expressions?

Java 8 – Functional Interfaces

• What is a functional interface in Java 8, and why are they important?
• Describe the use and benefits of the @FunctionalInterface annotation.
• Explain the purpose and use of the Predicate functional interface.
• How does the Function interface differ from the Consumer interface in Java 8?
• What are some real-world applications of the Supplier functional interface?
• Can you implement a custom functional interface and demonstrate how to use it with a lambda expression?
• How does method reference relate to functional interfaces in Java 8?
• What role do default methods play in functional interfaces?
• Describe how the BiFunction interface extends the capabilities of Function in Java 8.

Java 8 – Method References

• What are method references in Java 8, and how do they differ from lambda expressions?
• Can you demonstrate the use of method references by converting a lambda expression to a method reference for a static method?
• How would you describe method references that reference an instance method of a specific object, and when are they useful?
• Explain the usage of method references for an instance method of an arbitrary object of a particular type.
• Describe how constructor references work in Java 8, and when you would use them.
• What are the practical benefits of using method references over lambda expressions in Java 8?
• Illustrate how method references can be used in code dealing with collections and streams.
• What are some limitations or constraints of using method references compared to lambda expressions?
• How do method references support polymorphism in Java 8, particularly with functional interfaces?
• Can you explain the role of method references in enhancing performance compared to lambda expressions?

Java 8 – Stream API Basics

• What is a Stream in Java 8, and how do you create one?
• Explain the difference between intermediate and terminal operations in Streams.
• What is lazy evaluation in the context of Java Streams, and why is it beneficial?
• How would you use the `filter` operation in Streams, and what are its typical use cases?
• Explain the `map` operation and its difference from `flatMap` in Java Streams.
• How does the `reduce` operation work in Java Streams, and what are some common use cases?
• What is a Stream pipeline, and how does it function?
• How does Java 8 handle parallel stream processing, and what are some considerations when using it?
• What are the limitations of Java Streams, and how do you address them?

Java 8 – Advanced Stream API

• How does the `flatMap()` method differ from `map()` in Java Stream API, and when would you use one over the other?
• Can you explain how `Collectors.groupingBy` works in Java Streams and provide an example scenario where it would be beneficial?
• What is the purpose of `Collectors.partitioningBy` in Java Streams, and how does it differ from `groupingBy`?
• How can parallel streams improve performance in Java 8? Are there any potential downsides?
• What is a common pitfall when using streams in Java 8, specifically regarding stateful operations?
• Describe how you could optimize the performance of a stream pipeline in Java 8.
• What are the differences between a sequential and parallel stream, and which scenarios suit a parallel stream?
• Why should careful consideration be given to the order of operations in a stream pipeline?
• How can you apply a custom collector to process data with the Stream API, and why might this be useful?

Java 8 – Optional Class

• What is the Java 8 Optional class and why was it introduced?
• How does Optional help in avoiding NullPointerException (NPE) in Java applications?
• Can you explain the difference between `orElse()` and `orElseGet()` in Java's Optional class, along with a practical example of when to use each?
• Describe how you can use Optional to handle potentially null returning methods while adhering to functional programming principles?
• What are some common pitfalls when using the Optional class, and how can they be avoided?
• How can you use `ifPresent` and `ifPresentOrElse` to perform actions conditionally based on the presence of a value within Optional?
• Discuss the use of Optional in stream pipelines. How does it enhance code readability and maintain functional purity?
• What are some best practices for using the Optional class, particularly with respect to its efficiency and use cases?
• How does the Java 8 Optional class compare with traditional approaches of handling null in Java, and what are its typical limitations?

Java 8 – Default and Static Methods in Interfaces

• What are default methods in Java 8, and why were they introduced?
• Explain static methods in interfaces introduced in Java 8 and their uses.
• How do default methods handle multiple inheritance conflicts in Java 8?
• Can default methods in interfaces access non-static variables from classes that implement them? Why or why not?
• Discuss how Java 8 default methods impact backward compatibility.
• How are static methods in interfaces different from default methods, and what are their limitations?
• How do default and static methods in interfaces contribute to achieving functional programming in Java 8?
• How can lambda expressions interact with default and static methods in interfaces?
• Can you provide an example where default and static methods in an interface help resolve versioning issues in a library?
• In what scenarios would you prefer using default interface methods over abstract classes in Java 8?

Java 8 – Date and Time API

• What are some key differences between the Date and Time API in Java 8 versus the older java.util.Date and java.util.Calendar classes?
• How can you use the new Date and Time API to find the difference between two dates in years, months, and days?
• How can LocalTime be used to represent time-only data, and how is it manipulated without impacting date information?
• Explain the concept of ZonedDateTime and how it differs from LocalDateTime in the context of handling time zones.
• How can you parse and format dates using the DateTimeFormatter class in Java 8?
• Compare Period and Duration classes in Java 8. How do their applications differ?
• How does Java 8 ensure thread safety when working with the Date and Time API, and why is this important?
• What roles do TemporalAdjuster and TemporalAdjusters play in Java 8's Date and Time API, and how can they be practically applied?
• Explain how the Java 8 Date and Time API supports working with different chronologies and providing examples of when this is necessary.
• Describe how one would approach creating a custom temporal adjuster and provide an example of its use.

Java 8 – CompletableFuture

• What are CompletableFutures in Java 8, and how do they differ from Futures introduced in Java 5?
• Explain the use of `supplyAsync` in CompletableFuture with an example.
• How does thenApply differ from thenCompose, and when would you use each?
• What are some key strategies for combining multiple CompletableFutures?
• How does exception handling with CompletableFuture differ from traditional try-catch blocks?
• Describe the method `thenAccept` in CompletableFuture and provide an example of when it's appropriate to use it.
• Explain the mechanism of chaining CompletableFutures and discuss how it enhances efficiency over synchronous workflows.
• When should you use `runAsync` instead of `supplyAsync` in CompletableFuture?
• Discuss how you can manually complete a CompletableFuture and provide an example where it may be useful.
• Compare the concurrency capabilities of Java CompletableFuture API with parallel streams introduced in Java 8.

Java 8 – Parallel Streams and Fork/Join

Java 8 – Base64 and Misc Enhancements

Java 9 – Module System (Project Jigsaw)

Java 9 – Immutable Collections

Java 9 – Stream API Enhancements

Java 9 – Private Methods in Interfaces

Java 9 – JShell

Java 10 – Local Variable Type Inference (var)

Java 10 – Performance and JVM Improvements