Update #0 - First Release

sources/main/java/com/google/common/base/PairwiseEquivalence.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2011 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.base;
+
+import java.io.Serializable;
+import java.util.Iterator;
+
+import javax.annotation.Nullable;
+
+import com.google.common.annotations.GwtCompatible;
+
+@GwtCompatible(serializable = true)
+final class PairwiseEquivalence<T> extends Equivalence<Iterable<T>> implements Serializable {
+
+	final Equivalence<? super T> elementEquivalence;
+
+	PairwiseEquivalence(Equivalence<? super T> elementEquivalence) {
+		this.elementEquivalence = Preconditions.checkNotNull(elementEquivalence);
+	}
+
+	@Override
+	protected boolean doEquivalent(Iterable<T> iterableA, Iterable<T> iterableB) {
+		Iterator<T> iteratorA = iterableA.iterator();
+		Iterator<T> iteratorB = iterableB.iterator();
+
+		while (iteratorA.hasNext() && iteratorB.hasNext()) {
+			if (!elementEquivalence.equivalent(iteratorA.next(), iteratorB.next())) {
+				return false;
+			}
+		}
+
+		return !iteratorA.hasNext() && !iteratorB.hasNext();
+	}
+
+	@Override
+	protected int doHash(Iterable<T> iterable) {
+		int hash = 78721;
+		for (T element : iterable) {
+			hash = hash * 24943 + elementEquivalence.hash(element);
+		}
+		return hash;
+	}
+
+	@Override
+	public boolean equals(@Nullable Object object) {
+		if (object instanceof PairwiseEquivalence) {
+			PairwiseEquivalence<?> that = (PairwiseEquivalence<?>) object;
+			return this.elementEquivalence.equals(that.elementEquivalence);
+		}
+
+		return false;
+	}
+
+	@Override
+	public int hashCode() {
+		return elementEquivalence.hashCode() ^ 0x46a3eb07;
+	}
+
+	@Override
+	public String toString() {
+		return elementEquivalence + ".pairwise()";
+	}
+
+	private static final long serialVersionUID = 1;
+}