1 files changed, 64 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/util/CollectionHelper.java b/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/util/CollectionHelper.java
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index 00000000..6655be6d
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+++ b/subprojects/viatra-runtime-rete/src/main/java/tools/refinery/viatra/runtime/rete/itc/alg/util/CollectionHelper.java
@@ -0,0 +1,64 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2012, Tamas Szabo, Istvan Rath and Daniel Varro
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.rete.itc.alg.util;
+
+import tools.refinery.viatra.runtime.matchers.util.CollectionsFactory;
+
+import java.util.Set;
+
+/**
+ * @author Tamas Szabo
+ *
+ */
+public class CollectionHelper {
+
+    private CollectionHelper() {/*Utility class constructor*/}
+
+    /**
+     * Returns the intersection of two sets. It calls {@link Set#retainAll(java.util.Collection)} but returns a new set
+     * containing the elements of the intersection.
+     *
+     * @param set1
+     *            the first set (can be null, interpreted as empty)
+     * @param set2
+     *            the second set (can be null, interpreted as empty)
+     * @return the intersection of the sets
+     * @since 1.7
+     */
+    public static <V> Set<V> intersection(Set<V> set1, Set<V> set2) {
+        if (set1 == null || set2 == null)
+            return CollectionsFactory.createSet();
+
+        Set<V> intersection = CollectionsFactory.createSet(set1);
+        intersection.retainAll(set2);
+        return intersection;
+    }
+
+
+    /**
+     * Returns the difference of two sets (S1\S2). It calls {@link Set#removeAll(java.util.Collection)} but returns a
+     * new set containing the elements of the difference.
+     *
+     * @param set1
+     *            the first set (can be null, interpreted as empty)
+     * @param set2
+     *            the second set (can be null, interpreted as empty)
+     * @return the difference of the sets
+     * @since 1.7
+     */
+    public static <V> Set<V> difference(Set<V> set1, Set<V> set2) {
+        if (set1 == null)
+            return CollectionsFactory.createSet();
+
+        Set<V> difference = CollectionsFactory.createSet(set1);
+        if (set2 != null) difference.removeAll(set2);
+        return difference;
+    }
+
+}