前面的文章中说明了Java8中最基本的4种函数式接口，我们今天先介绍其它Supplier和Predicate以及Function函数式接口。

BooleanSupplier/DoubleSupplier/IntSupplier/LongSupplier

BooleanSupplier/DoubleSupplier/IntSupplier/LongSupplier这4个函数式接口，为获得基本类型的函数式接口。

BiPredicate

BiPredicate函数式接口的test方法接收2个参数。

/**
 * Represents a predicate (boolean-valued function) of two arguments.  This is
 * the two-arity specialization of {@link Predicate}.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #test(Object, Object)}.
 *
 * @param <T> the type of the first argument to the predicate
 * @param <U> the type of the second argument the predicate
 *
 * @see Predicate
 * @since 1.8
 */
@FunctionalInterface
public interface BiPredicate<T, U> {

    /**
     * Evaluates this predicate on the given arguments.
     *
     * @param t the first input argument
     * @param u the second input argument
     * @return {@code true} if the input arguments match the predicate,
     * otherwise {@code false}
     */
    boolean test(T t, U u);

    /**
     * Returns a composed predicate that represents a short-circuiting logical
     * AND of this predicate and another.  When evaluating the composed
     * predicate, if this predicate is {@code false}, then the {@code other}
     * predicate is not evaluated.
     *
     * <p>Any exceptions thrown during evaluation of either predicate are relayed
     * to the caller; if evaluation of this predicate throws an exception, the
     * {@code other} predicate will not be evaluated.
     *
     * @param other a predicate that will be logically-ANDed with this
     *              predicate
     * @return a composed predicate that represents the short-circuiting logical
     * AND of this predicate and the {@code other} predicate
     * @throws NullPointerException if other is null
     */
    default BiPredicate<T, U> and(BiPredicate<? super T, ? super U> other) {
        Objects.requireNonNull(other);
        return (T t, U u) -> test(t, u) && other.test(t, u);
    }

    /**
     * Returns a predicate that represents the logical negation of this
     * predicate.
     *
     * @return a predicate that represents the logical negation of this
     * predicate
     */
    default BiPredicate<T, U> negate() {
        return (T t, U u) -> !test(t, u);
    }

    /**
     * Returns a composed predicate that represents a short-circuiting logical
     * OR of this predicate and another.  When evaluating the composed
     * predicate, if this predicate is {@code true}, then the {@code other}
     * predicate is not evaluated.
     *
     * <p>Any exceptions thrown during evaluation of either predicate are relayed
     * to the caller; if evaluation of this predicate throws an exception, the
     * {@code other} predicate will not be evaluated.
     *
     * @param other a predicate that will be logically-ORed with this
     *              predicate
     * @return a composed predicate that represents the short-circuiting logical
     * OR of this predicate and the {@code other} predicate
     * @throws NullPointerException if other is null
     */
    default BiPredicate<T, U> or(BiPredicate<? super T, ? super U> other) {
        Objects.requireNonNull(other);
        return (T t, U u) -> test(t, u) || other.test(t, u);
    }
}

DoublePredicate/IntPredicate/LongPredicate

这几个函数式接口均是特殊化的Predicate接口

BiFunction

BiFunction与Function函数式接口的主要区别是：apply方法接收2个入参。

/**
 * Represents a function that accepts two arguments and produces a result.
 * This is the two-arity specialization of {@link Function}.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #apply(Object, Object)}.
 *
 * @param <T> the type of the first argument to the function
 * @param <U> the type of the second argument to the function
 * @param <R> the type of the result of the function
 *
 * @see Function
 * @since 1.8
 */
@FunctionalInterface
public interface BiFunction<T, U, R> {

    /**
     * Applies this function to the given arguments.
     *
     * @param t the first function argument
     * @param u the second function argument
     * @return the function result
     */
    R apply(T t, U u);

    /**
     * Returns a composed function that first applies this function to
     * its input, and then applies the {@code after} function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     *
     * @param <V> the type of output of the {@code after} function, and of the
     *           composed function
     * @param after the function to apply after this function is applied
     * @return a composed function that first applies this function and then
     * applies the {@code after} function
     * @throws NullPointerException if after is null
     */
    default <V> BiFunction<T, U, V> andThen(Function<? super R, ? extends V> after) {
        Objects.requireNonNull(after);
        return (T t, U u) -> after.apply(apply(t, u));
    }
}

DoubleFunction/IntFunction/LongFunction

DoubleFunction/IntFunction/LongFunction这三个函数式接口为特殊的Function接口。

LongToDoubleFunction/LongToIntFunction

LongToDoubleFunction/LongToIntFunction这两个函数式接口的apply方法为入参为long类型，出参为其它基本类型的Function。

ToDoubleFunction/ToIntFunction/ToLongFunction

ToDoubleFunction/ToIntFunction/ToLongFunction这三个函数式接口的apply方法为入参为其它类型，出参为基本类型的Function.

ToDoubleBiFunction/ToIntBiFunction/ToLongBiFunction

ToDoubleBiFunction/ToIntBiFunction/ToLongBiFunction这三个函数式接口的apply方法有2个入参，出参为基本类型的Function。