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diff --git a/src/main/java/org/apache/commons/lang3/builder/Diff.java b/src/main/java/org/apache/commons/lang3/builder/Diff.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.commons.lang3.builder;
+
+import java.lang.reflect.Type;
+
+import org.apache.commons.lang3.ObjectUtils;
+import org.apache.commons.lang3.reflect.TypeUtils;
+import org.apache.commons.lang3.tuple.Pair;
+
+/**
+ * A {@link Diff} contains the differences between two {@link Diffable} class
+ * fields.
+ *
+ * <p>
+ * Typically, {@link Diff}s are retrieved by using a {@link DiffBuilder} to
+ * produce a {@link DiffResult}, containing the differences between two objects.
+ * </p>
+ *
+ * @param <T>
+ *            The type of object contained within this {@link Diff}. Differences
+ *            between primitive objects are stored as their Object wrapper
+ *            equivalent.
+ * @since 3.3
+ */
+public abstract class Diff<T> extends Pair<T, T> {
+
+    private static final long serialVersionUID = 1L;
+
+    /** The field type. */
+    private final Type type;
+
+    /** The field name. */
+    private final String fieldName;
+
+    /**
+     * Constructs a new {@link Diff} for the given field name.
+     *
+     * @param fieldName
+     *            the field name
+     */
+    protected Diff(final String fieldName) {
+        this.type = ObjectUtils.defaultIfNull(
+                TypeUtils.getTypeArguments(getClass(), Diff.class).get(
+                        Diff.class.getTypeParameters()[0]), Object.class);
+        this.fieldName = fieldName;
+    }
+
+    /**
+     * Gets the type of the field.
+     *
+     * @return the field type
+     */
+    public final Type getType() {
+        return type;
+    }
+
+    /**
+     * Gets the name of the field.
+     *
+     * @return the field name
+     */
+    public final String getFieldName() {
+        return fieldName;
+    }
+
+    /**
+     * Returns a {@link String} representation of the {@link Diff}, with the
+     * following format:
+     *
+     * <pre>
+     * [fieldname: left-value, right-value]
+     * </pre>
+     *
+     * @return the string representation
+     */
+    @Override
+    public final String toString() {
+        return String.format("[%s: %s, %s]", fieldName, getLeft(), getRight());
+    }
+
+    /**
+     * Throws {@link UnsupportedOperationException}.
+     *
+     * @param value
+     *            ignored
+     * @return nothing
+     */
+    @Override
+    public final T setValue(final T value) {
+        throw new UnsupportedOperationException("Cannot alter Diff object.");
+    }
+}