Optional

Learn

Existing chapters for this concept.

• Streams & Optional

  Core Java

  💡 Streams are single-use — create a new stream for a second pipeline. Milestone: You completed Core APIs (chapters 16–20).

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See it in code

Existing Java examples.

• core 23 Optional Demo

  Core Java · pkg1core/core23OptionalDemo.java · pkg1core · core23OptionalDemo.java

  - Optional is a container that holds a value or nothing. - Prefer map/filter/flatMap + orElse/orElseThrow over isPresent()/get(). - Use it as a RETURN type;…

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• core22StreamsDemo

  Core Java · pkg1core/core22StreamsDemo.java · pkg1core · core22StreamsDemo.java

  - Streams are LAZY: intermediate ops (filter/map/sorted) build a pipeline; a terminal op (collect/reduce/forEach/count) triggers execution. - Streams don't…

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Prepare

Existing interview questions.

• What is `Optional`?

  Core Java — Interview Questions (200+)

  Clear naming, small methods, immutability, proper exceptions, tests, and idiomatic APIs.

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• Optional best practices?

  Functional Programming & Streams — Interview Questions (100+)

  Return type for "maybe"; chain map/filter; avoid get().

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• Stream to Optional reduce?

  Functional Programming & Streams — Interview Questions (100+)

  Keep lambdas pure, stateless, and non-interfering.

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• Optional vs exception for missing?

  Exceptions — Interview Questions (77+)

  @throws tags.

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• Optional.orElseThrow?

  Java 9–21 Features — Interview Questions (95+)

  infers raw-ish; specify generic.

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• Builder pattern for many optional parameters?

  Effective Java & Best Practices — Interview Questions (82+)

  Telescoping constructors are unreadable; Builder scales with fluency and validation.

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• Optional return from method?

  Effective Java & Best Practices — Interview Questions (82+)

  Named constants.

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Java versions

• Optional

  Java 8

  Java 8. modern, immutable date/time API.

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• Optional

  Final

  Optional. Optional is a return type for a value that may be absent. The stream chapter covers how to use it.

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Related concepts

Only explicit or deterministic relationships from the concept model.

• Exceptions

  Deterministic link

  co-mentioned in interview title: Optional vs exception for missing?

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