Chapter 8: Java 8 Features

Java 8 was the most monumental release in Java history, transitioning the language from strictly imperative and object-oriented paradigms into modern functional programming. With Lambda Expressions, Functional Interfaces, the Stream API, Optional null safety, and the Date/Time API, Java code became concise, expressive, and parallel-friendly.

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🧭 Subtopics & Curriculum

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Functional Core8.1

λ

8.1 Lambda Expressions

• What is a Lambda Expression?
• Different Lambda forms
  • No/Zero Parameter
  • Single Parameter
  • Multiple Parameters
  • Multiple Parameters with Inferred Types
  • Multi-line Body
• Lambda does NOT have a type by itself
• Why Functional Interface is required
• Lambda and Variable Scope
  • What does effectively final mean?
• Modern Java 8 Lambda:
• Version wise updates

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Contracts8.2

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8.2 Functional Interfaces

• What is a Functional Interface?
• Why do we need Functional Interface?
• Why exactly ONE abstract method?
• But can Functional Interface have other methods?
• What is @FunctionalInterface?
  • Is @FunctionalInterface mandatory?
• Common Functional Interfaces provided by Java
  • 1. Predicate<T>
  • 2. Function<T, R>
  • 3. Consumer<T>
  • 4. Supplier<T>

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Clean Syntax8.3

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8.3 Method References

• What is a Method Reference?
• Why was Method Reference introduced?
• Four Kinds of Method References
  • 1. Reference to a Static Method
  • 2. Reference to an Instance Method of a Particular Object
  • 3. Reference to an Instance Method of an Arbitrary Object of a Specific Type
  • 4. Reference to a Constructor
• Lambda vs Method Reference: When to Use What?

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Data Pipelines8.4

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8.4 Stream API

• What is Streams?
• Why was Stream API introduced?
• Streams vs Collections
• Stream Pipeline
• Intermediate Operations (Lazy)
  • map() vs flatMap():
• Terminal Operations (Eager)
• Version wise Updates
• Parallel Streams (Multithreading)

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Null Safety8.5

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8.5 Optional Class & Null Safety

• What is Optional Class?
• Creating Optional Instances
  • Optional.of()
  • Optional.ofNullable()
  • Optional.empty()
• Optional class method

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Modern Utilities8.6

⚙️

8.6 Default & Static Methods, Date/Time API & Other Features

• 1. Default & Static Methods in Interfaces
  • Default Methods (default keyword)
  • The Multiple Inheritance Conflict (Diamond Problem):
  • Static Methods in Interfaces:
• 2. Modern Date and Time API (java.time / JSR-310)
  • Practical Usage:
• 3. Native Base64 Encoding & Decoding (java.util.Base64)
• 4. Other Notable Java 8 Enhancements
  • String.join()
  • Repeating Annotations (@Repeatable)
  • Concurrency Upgrades:

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