79 lines
2.5 KiB
Java
79 lines
2.5 KiB
Java
package it.cavallium.strangedb.functionalinterfaces;
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import java.io.IOException;
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import java.util.Objects;
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/**
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* Represents a function that accepts one argument and produces a result.
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*
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* <p>This is a <a href="package-summary.html">functional interface</a>
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* whose functional method is {@link #apply(Object)}.
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*
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* @param <T> the type of the input to the function
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* @param <R> the type of the result of the function
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*
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* @since 1.8
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*/
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@FunctionalInterface
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public interface FunctionWithIO<T, R> {
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/**
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* Applies this function to the given argument.
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*
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* @param t the function argument
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* @return the function result
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*/
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R apply(T t) throws IOException;
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/**
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* Returns a composed function that first applies the {@code before}
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* function to its input, and then applies this function to the result.
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* If evaluation of either function throws an exception, it is relayed to
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* the caller of the composed function.
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*
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* @param <V> the type of input to the {@code before} function, and to the
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* composed function
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* @param before the function to apply before this function is applied
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* @return a composed function that first applies the {@code before}
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* function and then applies this function
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* @throws NullPointerException if before is null
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*
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* @see #andThen(FunctionWithIO)
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*/
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default <V> FunctionWithIO<V, R> compose(FunctionWithIO<? super V, ? extends T> before) {
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Objects.requireNonNull(before);
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return (V v) -> apply(before.apply(v));
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}
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/**
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* Returns a composed function that first applies this function to
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* its input, and then applies the {@code after} function to the result.
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* If evaluation of either function throws an exception, it is relayed to
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* the caller of the composed function.
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*
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* @param <V> the type of output of the {@code after} function, and of the
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* composed function
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* @param after the function to apply after this function is applied
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* @return a composed function that first applies this function and then
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* applies the {@code after} function
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* @throws NullPointerException if after is null
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*
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* @see #compose(FunctionWithIO)
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*/
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default <V> FunctionWithIO<T, V> andThen(FunctionWithIO<? super R, ? extends V> after) {
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Objects.requireNonNull(after);
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return (T t) -> after.apply(apply(t));
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}
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/**
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* Returns a function that always returns its input argument.
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*
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* @param <T> the type of the input and output objects to the function
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* @return a function that always returns its input argument
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*/
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static <T> FunctionWithIO<T, T> identity() {
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return t -> t;
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}
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}
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