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/**

 * <em>Functional interfaces</em> provide target types for lambda expressions

 * and method references.  Each functional interface has a single abstract method

 * to which the lambda expression's parameter and return types are matched or

 * adapted.  Functional interfaces can provide a target type in multiple contexts,

 * such as assignment context, method invocation, or cast context:

 *

 *

 *     stream.filter(e -> e.getSize() > 10)...

 *

 *     stream.map((ToIntFunction) e -> e.getSize())...

 *

 * <p>The interfaces in this package are functional interfaces used by the JDK,

 * and are available to be used by user code as well.  While they do not identify

 * a complete set of function shapes to which lambda expressions might be adapted,

 * they provide enough to cover common requirements.

 *

 * <p>The interfaces in this package are annotated with @{link FunctionalInterface}.

 * This annotation is not a requirement for the compiler to recognize an interface

 * as a functional interface, but merely an aid to capture design intent and enlist the

 * help of the compiler in identifying accidental violations of design intent.

 *

 * <p>The functional interfaces in this package follow an extensible naming convention,

 * as follows:

 *

 * <ul>

 *     <li>There are several basic function shapes, including {@link java.util.function.Function} ({@code T -> R}),

 *     {@link java.util.function.Consumer} ({@code T -> void}),

 *     {@link java.util.function.Predicate} ({@code T -> boolean}),

 *     and {@link java.util.function.Supplier} ({@code () -> T}).

 *     </li>

 *     <li>Function shapes have a natural arity based on how they are most commonly used.

 *     The basic shapes can be modified by an arity prefix to indicate a different arity,

 *     such as {@link java.util.function.BiFunction} ({@code (T, U) -> R}).

 *     </li>

 *     <li>There are additional derived function shapes which extend the basic function

 *     shapes, including {@link java.util.function.UnaryOperator} (extends {@code Function}) and

 *     {@link java.util.function.BinaryOperator} (extends {@code BiFunction}).

 *     </li>

 *     <li>Type parameters of functional interfaces can be specialized to primitives with

 *     additional type prefixes.  To specialize the return type for a type that has both

 *     generic return type and generic arguments, we prefix {@code ToXxx}, as in

 *     {@link java.util.function.ToIntFunction}.  Otherwise, type arguments are specialized left-to-right,

 *     as in {@link java.util.function.DoubleConsumer} or {@link java.util.function.ObjIntConsumer}.

 *     (The type prefix {@code Obj} is used to indicate that we don't want to specialize this parameter,

 *     but want to move on to the next parameter.)  These schemes can be combined as in {@code IntToDoubleFunction}.

 *     </li>

 *     <li>If there are specialization prefixes for all arguments, the arity prefix may be left

 *     out (as in {@link java.util.function.ObjIntConsumer}).

 *     </li>

 * </ul>

 *

 * @see java.lang.FunctionalInterface

 */

package java.util.function;