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Streams intermediate

Optional.or() fallback

Chain Optional fallbacks without nested checks.

Code Comparison
✕ Java 8 
Optional<Config> cfg = primary();
if (!cfg.isPresent()) {
    cfg = secondary();
}
if (!cfg.isPresent()) {
    cfg = defaults();
}
✓ Java 9+ 
Optional<Config> cfg = primary()
    .or(this::secondary)
    .or(this::defaults);
Why the modern way wins
🔗

Chainable

Stack fallbacks in a readable pipeline.

⚡

Lazy evaluation

Fallback suppliers only execute if needed.

📖

Declarative

Reads as 'try primary, or secondary, or defaults'.

Old Approach
Nested Fallback
Modern Approach
.or() chain
Since JDK
9
Difficulty
intermediate
JDK Support
Optional.or() fallback
Available

Widely available since JDK 9 (Sept 2017)

How it works

Optional.or() returns the original Optional if it has a value, otherwise evaluates the supplier to get an alternative Optional. Suppliers are lazy — only called when needed.

Related patterns

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Stream.iterate(1, n -> n * 2)
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Java 9+
Stream.iterate(
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).forEach(System.out::println);
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// Sliding window: manual implementation
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Java 24+
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        Gatherers.windowSliding(3)
    )
    .toList();
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Stream.ofNullable()

Java 8
Stream<String> s = val != null
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Java 9+
Stream<String> s =
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JDK 9+ →
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