241 lines
8.2 KiB
Java
241 lines
8.2 KiB
Java
/*
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* Minecraft Forge
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* Copyright (c) 2016-2018.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation version 2.1
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* of the License.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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package net.minecraftforge.fml;
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import java.util.NoSuchElementException;
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import java.util.Objects;
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import java.util.Optional;
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import java.util.function.Consumer;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.function.Supplier;
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public final class OptionalMod<T>
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{
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private final String modId;
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private T value;
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private boolean searched;
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public static <M> OptionalMod<M> of(final String modId) {
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return new OptionalMod<>(modId);
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}
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private static OptionalMod<?> EMPTY = new OptionalMod<>(true);
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private static <T> OptionalMod<T> empty() {
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@SuppressWarnings("unchecked")
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OptionalMod<T> t = (OptionalMod<T>) EMPTY;
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return t;
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}
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private OptionalMod(boolean searched) {
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this.searched = searched;
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this.modId = "";
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}
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private OptionalMod(String modId)
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{
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this.modId = modId;
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}
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private T getValue()
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{
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if (!searched) {
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this.value = ModList.get().<T>getModObjectById(this.modId).orElse(null);
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searched = true;
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}
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return this.value;
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}
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/**
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* If a mod is present in this {@code OptionalMod}, returns the value,
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* otherwise throws {@code NoSuchElementException}.
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*
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* @return the modobject held by this {@code OptionalMod}
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* @throws NoSuchElementException if there is no modobject present
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*
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* @see Optional#isPresent()
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*/
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public T get() {
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if (getValue() == null) {
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throw new NoSuchElementException("No value present");
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}
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return getValue();
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}
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public String getModId() {
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return this.modId;
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}
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/**
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* Return {@code true} if there is a mod object present, otherwise {@code false}.
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*
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* @return {@code true} if there is a mod object present, otherwise {@code false}
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*/
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public boolean isPresent() {
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return getValue() != null;
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}
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/**
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* If a mod object is present, invoke the specified consumer with the object,
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* otherwise do nothing.
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*
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* @param consumer block to be executed if a mod object is present
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* @throws NullPointerException if mod object is present and {@code consumer} is
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* null
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*/
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public void ifPresent(Consumer<? super T> consumer) {
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if (getValue() != null)
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consumer.accept(getValue());
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}
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/**
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* If a mod object is present, and the mod object matches the given predicate,
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* return an {@code OptionalMod} describing the value, otherwise return an
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* empty {@code OptionalMod}.
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*
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* @param predicate a predicate to apply to the mod object, if present
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* @return an {@code OptionalMod} describing the value of this {@code OptionalMod}
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* if a mod object is present and the mod object matches the given predicate,
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* otherwise an empty {@code OptionalMod}
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* @throws NullPointerException if the predicate is null
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*/
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public OptionalMod<T> filter(Predicate<? super T> predicate) {
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Objects.requireNonNull(predicate);
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if (!isPresent())
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return this;
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else
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return predicate.test(getValue()) ? this : empty();
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}
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/**
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* If a mod object is present, apply the provided mapping function to it,
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* and if the result is non-null, return an {@code Optional} describing the
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* result. Otherwise return an empty {@code Optional}.
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*
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* @apiNote This method supports post-processing on optional values, without
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* the need to explicitly check for a return status.
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*
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* @param <U> The type of the result of the mapping function
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* @param mapper a mapping function to apply to the mod object, if present
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* @return an {@code Optional} describing the result of applying a mapping
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* function to the mod object of this {@code OptionalMod}, if a mod object is present,
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* otherwise an empty {@code Optional}
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* @throws NullPointerException if the mapping function is null
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*/
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public<U> Optional<U> map(Function<? super T, ? extends U> mapper) {
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Objects.requireNonNull(mapper);
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if (!isPresent())
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return Optional.empty();
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else {
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return Optional.ofNullable(mapper.apply(getValue()));
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}
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}
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/**
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* If a value is present, apply the provided {@code Optional}-bearing
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* mapping function to it, return that result, otherwise return an empty
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* {@code Optional}. This method is similar to {@link #map(Function)},
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* but the provided mapper is one whose result is already an {@code Optional},
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* and if invoked, {@code flatMap} does not wrap it with an additional
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* {@code Optional}.
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*
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* @param <U> The type parameter to the {@code Optional} returned by
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* @param mapper a mapping function to apply to the mod object, if present
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* the mapping function
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* @return the result of applying an {@code Optional}-bearing mapping
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* function to the value of this {@code Optional}, if a value is present,
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* otherwise an empty {@code Optional}
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* @throws NullPointerException if the mapping function is null or returns
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* a null result
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*/
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public<U> Optional<U> flatMap(Function<? super T, Optional<U>> mapper) {
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Objects.requireNonNull(mapper);
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if (!isPresent())
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return Optional.empty();
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else {
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return Objects.requireNonNull(mapper.apply(getValue()));
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}
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}
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/**
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* Return the mod object if present, otherwise return {@code other}.
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*
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* @param other the mod object to be returned if there is no mod object present, may
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* be null
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* @return the mod object, if present, otherwise {@code other}
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*/
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public T orElse(T other) {
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return getValue() != null ? getValue() : other;
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}
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/**
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* Return the mod object if present, otherwise invoke {@code other} and return
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* the result of that invocation.
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*
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* @param other a {@code Supplier} whose result is returned if no mod object
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* is present
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* @return the mod object if present otherwise the result of {@code other.get()}
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* @throws NullPointerException if mod object is not present and {@code other} is
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* null
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*/
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public T orElseGet(Supplier<? extends T> other) {
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return getValue() != null ? getValue() : other.get();
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}
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/**
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* Return the contained mod object, if present, otherwise throw an exception
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* to be created by the provided supplier.
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*
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* @apiNote A method reference to the exception constructor with an empty
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* argument list can be used as the supplier. For example,
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* {@code IllegalStateException::new}
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*
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* @param <X> Type of the exception to be thrown
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* @param exceptionSupplier The supplier which will return the exception to
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* be thrown
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* @return the present mod object
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* @throws X if there is no mod object present
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* @throws NullPointerException if no mod object is present and
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* {@code exceptionSupplier} is null
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*/
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public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {
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if (getValue() != null) {
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return getValue();
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} else {
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throw exceptionSupplier.get();
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}
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}
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@Override
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public boolean equals(Object obj)
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{
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if (this == obj) return true;
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if (obj instanceof OptionalMod) {
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return Objects.equals(((OptionalMod)obj).modId, modId);
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}
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return false;
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}
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@Override
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public int hashCode()
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{
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return Objects.hashCode(modId);
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}
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}
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