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package gregtech.api.objects;
import java.util.Map;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;
public class CollectorUtils {
/**
* Returns a merge function, suitable for use in
* {@link Map#merge(Object, Object, BiFunction) Map.merge()} or
* {@link Collectors#toMap(Function, Function, BinaryOperator) toMap()}, which always
* throws {@code IllegalStateException}. This can be used to enforce the
* assumption that the elements being collected are distinct.
*
* @param <T> the type of input arguments to the merge function
* @return a merge function which always throw {@code IllegalStateException}
*/
public static <T> BinaryOperator<T> throwingMerger() {
return (u, v) -> {
throw new IllegalStateException(String.format("Duplicate key %s", u));
};
}
public static <K, V, E extends Map.Entry<K, V>, M extends Map<K, V>> Collector<E, ?, M> entriesToMap(
Supplier<M> mapSupplier) {
return Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, CollectorUtils.throwingMerger(), mapSupplier);
}
}
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