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/*
 * SonarSource Analyzers Commons
 * Copyright (C) 2009-2025 SonarSource SA
 * mailto:info AT sonarsource DOT com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the Sonar Source-Available License Version 1, as published by SonarSource SA.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the Sonar Source-Available License for more details.
 *
 * You should have received a copy of the Sonar Source-Available License
 * along with this program; if not, see https://sonarsource.com/license/ssal/
 */
package org.sonarsource.analyzer.commons.collections;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.stream.Collectors;

/**
 * This class is used for Java < 9 to simplify the creation of maps.
 * After moving to Java > 9, should be replaced by Immutable Set Static Factory Methods
 * @see Immutable Set Static Factory Methods
 */
public final class SetUtils {

  private SetUtils() {
  }

  @SafeVarargs
  public static  Set immutableSetOf(T ... elements) {
    Set set = new HashSet<>(Arrays.asList(elements));
    return Collections.unmodifiableSet(set);
  }

  @SafeVarargs
  public static  Set concat(Set... sets) {
    return Arrays.stream(sets)
      .flatMap(Set::stream)
      .collect(Collectors.toSet());
  }

  public static  Set difference(Set set1, Set set2) {
    Set newSet1 = new HashSet<>(set1);
    newSet1.removeAll(set2);
    return newSet1;
  }

  public static  T getOnlyElement(Set set) {
    if (set.size() == 1) {
      return set.iterator().next();
    }
    throw new IllegalArgumentException(String.format("Expected set of size 1, but was set of size %d.", set.size()));
  }

}