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Streams beginner

Stream.ofNullable()

Create a zero-or-one element stream from a nullable value.

Code Comparison
✕ Java 8 
Stream<String> s = val != null
    ? Stream.of(val)
    : Stream.empty();
✓ Java 9+ 
Stream<String> s =
    Stream.ofNullable(val);
Why the modern way wins
📏

Concise

One call replaces the ternary conditional.

🔗

Flatmap-friendly

Perfect inside flatMap to skip null values.

🛡️

Null-safe

No NPE risk — null becomes empty stream.

Old Approach
Null Check
Modern Approach
ofNullable()
Since JDK
9
Difficulty
beginner
JDK Support
Stream.ofNullable()
Available

Widely available since JDK 9 (Sept 2017)

How it works

Stream.ofNullable() returns a single-element stream if the value is non-null, or an empty stream if null. Eliminates the ternary null check pattern.

Related patterns

Streams beginner

Stream takeWhile / dropWhile

Java 8
List<Integer> result = new ArrayList<>();
for (int n : sorted) {
    if (n >= 100) break;
    result.add(n);
}
// no stream equivalent in Java 8
Java 9+
var result = sorted.stream()
    .takeWhile(n -> n < 100)
    .toList();
// or: .dropWhile(n -> n < 10)
Hover to see modern ➜
JDK 9+ →
Streams intermediate

Stream.iterate() with predicate

Java 8
Stream.iterate(1, n -> n * 2)
    .limit(10)
    .forEach(System.out::println);
// can't stop at a condition
Java 9+
Stream.iterate(
    1,
    n -> n < 1000,
    n -> n * 2
).forEach(System.out::println);
// stops when n >= 1000
Hover to see modern ➜
JDK 9+ →
Streams advanced

Stream gatherers

Java 8
// Sliding window: manual implementation
List<List<T>> windows = new ArrayList<>();
for (int i = 0; i <= list.size()-3; i++) {
    windows.add(
        list.subList(i, i + 3));
}
Java 24+
var windows = stream
    .gather(
        Gatherers.windowSliding(3)
    )
    .toList();
Hover to see modern ➜
JDK 24+ →
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