⚡

Stream API & Lambdas

Declarative data processing and functional interfaces.

Pipeline shape

list.stream()          // source
  .filter(x -> x > 0)  // intermediate
  .map(x -> x * 2)     // intermediate
  .toList();           // terminal

Common operations

```
filter(pred)
```
keep matching
```
map(fn)
```
transform each
```
reduce(0, Integer::sum)
```
combine to one
```
sorted() / distinct() / limit(n)
```
```
count() / findFirst() / anyMatch(pred)
```

Collectors

```
collect(Collectors.toList())
```
```
Collectors.groupingBy(X::key)
```
```
Collectors.joining(", ")
```
```
Collectors.averagingInt / summingDouble
```

Functional interfaces

```
Function<T,R>
```
T -> R
```
Predicate<T>
```
T -> boolean
```
Consumer<T>
```
T -> void
```
Supplier<T>
```
() -> T
```
String::length
```
method reference