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Hibernate's core ORM functionality

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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later
 * See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
 */
package org.hibernate.internal.util;

import java.util.function.Supplier;

/**
 * @author Steve Ebersole
 */
public class NullnessHelper {
	private NullnessHelper() {
	}

	public static  T nullif(T test, T fallback) {
		return coalesce( test, fallback );
	}

	public static  T nullif(T test, Supplier fallbackSupplier) {
		return test != null ? test : fallbackSupplier.get();
	}

	/**
	 * Operates like SQL coalesce expression, returning the first non-empty value
	 *
	 * @implNote This impl treats empty strings (`""`) as null.
	 *
	 * @param values The list of values.
	 * @param  Generic type of values to coalesce
	 *
	 * @return The first non-empty value, or null if all values were empty
	 */
	@SafeVarargs
	public static  T coalesce(T... values) {
		if ( values == null ) {
			return null;
		}
		for ( T value : values ) {
			if ( value != null ) {
				if ( value instanceof String ) {
					if ( StringHelper.isNotEmpty( (String) value ) ) {
						return value;
					}
				}
				else {
					return value;
				}
			}
		}

		return null;
	}

	/**
	 * Operates like SQL coalesce expression, returning the first non-empty value
	 *
	 * @implNote This impl treats empty strings (`""`) as null.
	 *
	 * @param valueSuppliers List of value Suppliers
	 * @param  Generic type of values to coalesce
	 *
	 * @return The first non-empty value, or null if all values were empty
	 */
	@SafeVarargs
	public static  T coalesceSuppliedValues(Supplier... valueSuppliers) {
		if ( valueSuppliers == null ) {
			return null;
		}
		for ( Supplier valueSupplier : valueSuppliers ) {
			if ( valueSupplier != null ) {
				final T value = valueSupplier.get();
				if ( value instanceof String ) {
					if ( StringHelper.isNotEmpty( (String) value ) ) {
						return value;
					}
				}
				else if ( value != null ) {
					return value;
				}
			}
		}

		return null;
	}
}