Java tutorial
/* * Copyright (c) 2016 Gridtec. All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package at.gridtec.lambda4j.function.bi; import at.gridtec.lambda4j.Lambda; import at.gridtec.lambda4j.consumer.bi.BiDoubleConsumer; import at.gridtec.lambda4j.function.DoubleFunction2; import at.gridtec.lambda4j.function.conversion.BooleanToDoubleFunction; import at.gridtec.lambda4j.function.conversion.ByteToDoubleFunction; import at.gridtec.lambda4j.function.conversion.CharToDoubleFunction; import at.gridtec.lambda4j.function.conversion.FloatToDoubleFunction; import at.gridtec.lambda4j.function.conversion.ShortToDoubleFunction; import org.apache.commons.lang3.tuple.Pair; import javax.annotation.Nonnegative; import javax.annotation.Nonnull; import javax.annotation.Nullable; import java.util.Map; import java.util.Objects; import java.util.Optional; import java.util.concurrent.ConcurrentHashMap; import java.util.function.Consumer; import java.util.function.DoubleFunction; import java.util.function.DoubleUnaryOperator; import java.util.function.Function; import java.util.function.IntToDoubleFunction; import java.util.function.LongToDoubleFunction; import java.util.function.ToDoubleFunction; /** * Represents an operation that accepts two {@code double}-valued input arguments and produces a * result. * This is a primitive specialization of {@link BiFunction2}. * <p> * This is a {@link FunctionalInterface} whose functional method is {@link #apply(double, double)}. * * @param <R> The type of return value from the function * @see BiFunction2 */ @SuppressWarnings("unused") @FunctionalInterface public interface BiDoubleFunction<R> extends Lambda { /** * Constructs a {@link BiDoubleFunction} based on a lambda expression or a method reference. Thereby the given * lambda expression or method reference is returned on an as-is basis to implicitly transform it to the desired * type. With this method, it is possible to ensure that correct type is used from lambda expression or method * reference. * * @param <R> The type of return value from the function * @param expression A lambda expression or (typically) a method reference, e.g. {@code this::method} * @return A {@code BiDoubleFunction} from given lambda expression or method reference. * @implNote This implementation allows the given argument to be {@code null}, but only if {@code null} given, * {@code null} will be returned. * @see <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html#syntax">Lambda * Expression</a> * @see <a href="https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html">Method Reference</a> */ static <R> BiDoubleFunction<R> of(@Nullable final BiDoubleFunction<R> expression) { return expression; } /** * Lifts a partial {@link BiDoubleFunction} into a total {@link BiDoubleFunction} that returns an {@link Optional} * result. * * @param <R> The type of return value from the function * @param partial A function that is only defined for some values in its domain * @return A partial {@code BiDoubleFunction} lifted into a total {@code BiDoubleFunction} that returns an {@code * Optional} result. * @throws NullPointerException If given argument is {@code null} */ @Nonnull static <R> BiDoubleFunction<Optional<R>> lift(@Nonnull final BiDoubleFunction<? extends R> partial) { Objects.requireNonNull(partial); return (value1, value2) -> Optional.ofNullable(partial.apply(value1, value2)); } /** * Calls the given {@link BiDoubleFunction} with the given arguments and returns its result. * * @param <R> The type of return value from the function * @param function The function to be called * @param value1 The first argument to the function * @param value2 The second argument to the function * @return The result from the given {@code BiDoubleFunction}. * @throws NullPointerException If given argument is {@code null} */ static <R> R call(@Nonnull final BiDoubleFunction<? extends R> function, double value1, double value2) { Objects.requireNonNull(function); return function.apply(value1, value2); } /** * Creates a {@link BiDoubleFunction} which uses the {@code first} parameter of this one as argument for the given * {@link DoubleFunction}. * * @param <R> The type of return value from the function * @param function The function which accepts the {@code first} parameter of this one * @return Creates a {@code BiDoubleFunction} which uses the {@code first} parameter of this one as argument for the * given {@code DoubleFunction}. * @throws NullPointerException If given argument is {@code null} */ @Nonnull static <R> BiDoubleFunction<R> onlyFirst(@Nonnull final DoubleFunction<? extends R> function) { Objects.requireNonNull(function); return (value1, value2) -> function.apply(value1); } /** * Creates a {@link BiDoubleFunction} which uses the {@code second} parameter of this one as argument for the given * {@link DoubleFunction}. * * @param <R> The type of return value from the function * @param function The function which accepts the {@code second} parameter of this one * @return Creates a {@code BiDoubleFunction} which uses the {@code second} parameter of this one as argument for * the given {@code DoubleFunction}. * @throws NullPointerException If given argument is {@code null} */ @Nonnull static <R> BiDoubleFunction<R> onlySecond(@Nonnull final DoubleFunction<? extends R> function) { Objects.requireNonNull(function); return (value1, value2) -> function.apply(value2); } /** * Creates a {@link BiDoubleFunction} which always returns a given value. * * @param <R> The type of return value from the function * @param ret The return value for the constant * @return A {@code BiDoubleFunction} which always returns a given value. */ @Nonnull static <R> BiDoubleFunction<R> constant(R ret) { return (value1, value2) -> ret; } /** * Applies this function to the given arguments. * * @param value1 The first argument to the function * @param value2 The second argument to the function * @return The return value from the function, which is its result. */ R apply(double value1, double value2); /** * Applies this function partially to some arguments of this one, producing a {@link DoubleFunction2} as result. * * @param value1 The first argument to this function used to partially apply this function * @return A {@code DoubleFunction2} that represents this function partially applied the some arguments. */ @Nonnull default DoubleFunction2<R> papply(double value1) { return (value2) -> this.apply(value1, value2); } /** * Returns the number of arguments for this function. * * @return The number of arguments for this function. * @implSpec The default implementation always returns {@code 2}. */ @Nonnegative default int arity() { return 2; } /** * Returns a composed {@link BiFunction2} that first applies the {@code before} functions to its input, and * then applies this function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * * @param <A> The type of the argument to the first given function, and of composed function * @param <B> The type of the argument to the second given function, and of composed function * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiFunction2} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is able to handle every type. */ @Nonnull default <A, B> BiFunction2<A, B, R> compose(@Nonnull final ToDoubleFunction<? super A> before1, @Nonnull final ToDoubleFunction<? super B> before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (a, b) -> apply(before1.applyAsDouble(a), before2.applyAsDouble(b)); } /** * Returns a composed {@link BiBooleanFunction} that first applies the {@code before} functions to its input, and * then applies this function to the result. If evaluation of either operation throws an exception, it is relayed to * the caller of the composed operation. This method is just convenience, to provide the ability to execute an * operation which accepts {@code boolean} input, before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiBooleanFunction} that first applies the {@code before} functions to its input, and * then applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * boolean}. */ @Nonnull default BiBooleanFunction<R> composeFromBoolean(@Nonnull final BooleanToDoubleFunction before1, @Nonnull final BooleanToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiByteFunction} that first applies the {@code before} functions to * its input, and then applies this function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * This method is just convenience, to provide the ability to execute an operation which accepts {@code byte} input, * before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiByteFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * byte}. */ @Nonnull default BiByteFunction<R> composeFromByte(@Nonnull final ByteToDoubleFunction before1, @Nonnull final ByteToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiCharFunction} that first applies the {@code before} functions to * its input, and then applies this function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * This method is just convenience, to provide the ability to execute an operation which accepts {@code char} input, * before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiCharFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * char}. */ @Nonnull default BiCharFunction<R> composeFromChar(@Nonnull final CharToDoubleFunction before1, @Nonnull final CharToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiDoubleFunction} that first applies the {@code before} operators to its input, and * then applies this function to the result. If evaluation of either operation throws an exception, it is relayed to * the caller of the composed operation. This method is just convenience, to provide the ability to execute an * operation which accepts {@code double} input, before this primitive function is executed. * * @param before1 The first operator to apply before this function is applied * @param before2 The second operator to apply before this function is applied * @return A composed {@code BiDoubleFunction} that first applies the {@code before} operators to its input, and * then applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * double}. */ @Nonnull default BiDoubleFunction<R> composeFromDouble(@Nonnull final DoubleUnaryOperator before1, @Nonnull final DoubleUnaryOperator before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiFloatFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. If evaluation of either operation throws an exception, it is relayed to the * caller of the composed operation. This method is just convenience, to provide the ability to execute an operation * which accepts {@code float} input, before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiFloatFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * float}. */ @Nonnull default BiFloatFunction<R> composeFromFloat(@Nonnull final FloatToDoubleFunction before1, @Nonnull final FloatToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiIntFunction} that first applies the {@code before} functions to * its input, and then applies this function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * This method is just convenience, to provide the ability to execute an operation which accepts {@code int} input, * before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiIntFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * int}. */ @Nonnull default BiIntFunction<R> composeFromInt(@Nonnull final IntToDoubleFunction before1, @Nonnull final IntToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiLongFunction} that first applies the {@code before} functions to * its input, and then applies this function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * This method is just convenience, to provide the ability to execute an operation which accepts {@code long} input, * before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiLongFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * long}. */ @Nonnull default BiLongFunction<R> composeFromLong(@Nonnull final LongToDoubleFunction before1, @Nonnull final LongToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiShortFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. If evaluation of either operation throws an exception, it is relayed to the * caller of the composed operation. This method is just convenience, to provide the ability to execute an operation * which accepts {@code short} input, before this primitive function is executed. * * @param before1 The first function to apply before this function is applied * @param before2 The second function to apply before this function is applied * @return A composed {@code BiShortFunction} that first applies the {@code before} functions to its input, and then * applies this function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is a able to handle primitive values. In this case this is {@code * short}. */ @Nonnull default BiShortFunction<R> composeFromShort(@Nonnull final ShortToDoubleFunction before1, @Nonnull final ShortToDoubleFunction before2) { Objects.requireNonNull(before1); Objects.requireNonNull(before2); return (value1, value2) -> apply(before1.applyAsDouble(value1), before2.applyAsDouble(value2)); } /** * Returns a composed {@link BiDoubleFunction} that first applies this function to its input, and then applies the * {@code after} function to the result. * If evaluation of either operation throws an exception, it is relayed to the caller of the composed operation. * * @param <S> The type of return value from the {@code after} function, and of the composed function * @param after The function to apply after this function is applied * @return A composed {@code BiDoubleFunction} that first applies this function to its input, and then applies the * {@code after} function to the result. * @throws NullPointerException If given argument is {@code null} * @implSpec The input argument of this method is able to return every type. */ @Nonnull default <S> BiDoubleFunction<S> andThen(@Nonnull final Function<? super R, ? extends S> after) { Objects.requireNonNull(after); return (value1, value2) -> after.apply(apply(value1, value2)); } /** * Returns a composed {@link BiDoubleConsumer} that fist applies this function to its input, and then consumes the * result using the given {@link Consumer}. If evaluation of either operation throws an exception, it is relayed to * the caller of the composed operation. * * @param consumer The operation which consumes the result from this operation * @return A composed {@code BiDoubleConsumer} that first applies this function to its input, and then consumes the * result using the given {@code Consumer}. * @throws NullPointerException If given argument is {@code null} */ @Nonnull default BiDoubleConsumer consume(@Nonnull final Consumer<? super R> consumer) { Objects.requireNonNull(consumer); return (value1, value2) -> consumer.accept(apply(value1, value2)); } /** * Returns a memoized (caching) version of this {@link BiDoubleFunction}. Whenever it is called, the mapping between * the input parameters and the return value is preserved in a cache, making subsequent calls returning the memoized * value instead of computing the return value again. * <p> * Unless the function and therefore the used cache will be garbage-collected, it will keep all memoized values * forever. * * @return A memoized (caching) version of this {@code BiDoubleFunction}. * @implSpec This implementation does not allow the input parameters or return value to be {@code null} for the * resulting memoized function, as the cache used internally does not permit {@code null} keys or values. * @implNote The returned memoized function can be safely used concurrently from multiple threads which makes it * thread-safe. */ @Nonnull default BiDoubleFunction<R> memoized() { if (isMemoized()) { return this; } else { final Map<Pair<Double, Double>, R> cache = new ConcurrentHashMap<>(); final Object lock = new Object(); return (BiDoubleFunction<R> & Memoized) (value1, value2) -> { final R returnValue; synchronized (lock) { returnValue = cache.computeIfAbsent(Pair.of(value1, value2), key -> apply(key.getLeft(), key.getRight())); } return returnValue; }; } } /** * Converts this function to an equal function, which ensures that its result is not * {@code null} using {@link Optional}. This method mainly exists to avoid unnecessary {@code NullPointerException}s * through referencing {@code null} from this function. * * @return An equal function, which ensures that its result is not {@code null}. * @deprecated Use {@code lift} method for lifting this function. */ @Deprecated @Nonnull default BiDoubleFunction<Optional<R>> nonNull() { return (value1, value2) -> Optional.ofNullable(apply(value1, value2)); } /** * Returns a composed {@link BiFunction2} which represents this {@link BiDoubleFunction}. Thereby the primitive * input argument for this function is autoboxed. This method provides the possibility to use this * {@code BiDoubleFunction} with methods provided by the {@code JDK}. * * @return A composed {@code BiFunction2} which represents this {@code BiDoubleFunction}. */ @Nonnull default BiFunction2<Double, Double, R> boxed() { return this::apply; } }