%5Bid%5D/page-600f54cc3a48e9b9.js"],"Image"] 1c:T76b,The six basic functional interfaces in Java 8 form the foundation of the functional programming API: 1. **UnaryOperator\** - Purpose: Takes a T and returns a T (same type input/output) - Method: `T apply(T t)` - Example: `String::toLowerCase` - Primitive variants: `IntUnaryOperator`, `LongUnaryOperator`, `DoubleUnaryOperator` 2. **BinaryOperator\** - Purpose: Takes two Ts and returns a T - Method: `T apply(T t1, T t2)` - Example: `BigInteger::add` - Primitive variants: `IntBinaryOperator`, `LongBinaryOperator`, `DoubleBinaryOperator` 3. **Predicate\** - Purpose: Takes a T and returns a boolean - Method: `boolean test(T t)` - Example: `Collection::isEmpty` - Primitive variants: `IntPredicate`, `LongPredicate`, `DoublePredicate` 4. **Function\** - Purpose: Takes a T and returns an R (different input/output types) - Method: `R apply(T t)` - Example: `Arrays::asList` - Primitive variants include: - Type to primitive: `ToIntFunction`, `ToLongFunction`, `ToDoubleFunction` - Primitive to type: `IntFunction`, `LongFunction`, `DoubleFunction` - Primitive to primitive: `IntToLongFunction`, `IntToDoubleFunction`, etc. 5. **Supplier\** - Purpose: Takes no arguments and returns a T - Method: `T get()` - Example: `Instant::now` - Primitive variants: `IntSupplier`, `LongSupplier`, `DoubleSupplier`, `BooleanSupplier` 6. **Consumer\** - Purpose: Takes a T and returns nothing (void) - Method: `void accept(T t)` - Example: `System.out::println` - Primitive variants: `IntConsumer`, `LongConsumer`, `DoubleConsumer` **Key point**: There are 43 interfaces in `java.util.function`, but most are variations of these six basic interfaces. When designing APIs that accept functional objects, prefer these standard interfaces over creating custom functional interfaces.1d:T855,

Lambdas and Streams

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