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diff --git a/guava/src/com/google/common/primitives/Primitives.java b/guava/src/com/google/common/primitives/Primitives.java
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+/*
+ * Copyright (C) 2007 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.primitives;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Contains static utility methods pertaining to primitive types and their
+ * corresponding wrapper types.
+ *
+ * @author Kevin Bourrillion
+ * @since 1.0
+ */
+public final class Primitives {
+  private Primitives() {}
+
+  /** A map from primitive types to their corresponding wrapper types. */
+  private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;
+
+  /** A map from wrapper types to their corresponding primitive types. */
+  private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;
+
+  // Sad that we can't use a BiMap. :(
+  
+  static {
+    Map<Class<?>, Class<?>> primToWrap = new HashMap<Class<?>, Class<?>>(16);
+    Map<Class<?>, Class<?>> wrapToPrim = new HashMap<Class<?>, Class<?>>(16);
+
+    add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
+    add(primToWrap, wrapToPrim, byte.class, Byte.class);
+    add(primToWrap, wrapToPrim, char.class, Character.class);
+    add(primToWrap, wrapToPrim, double.class, Double.class);
+    add(primToWrap, wrapToPrim, float.class, Float.class);
+    add(primToWrap, wrapToPrim, int.class, Integer.class);
+    add(primToWrap, wrapToPrim, long.class, Long.class);
+    add(primToWrap, wrapToPrim, short.class, Short.class);
+    add(primToWrap, wrapToPrim, void.class, Void.class);
+
+    PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
+    WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
+  }
+
+  private static void add(Map<Class<?>, Class<?>> forward,
+      Map<Class<?>, Class<?>> backward, Class<?> key, Class<?> value) {
+    forward.put(key, value);
+    backward.put(value, key);
+  }
+
+  /**
+   * Returns an immutable set of all nine primitive types (including {@code
+   * void}). Note that a simpler way to test whether a {@code Class} instance
+   * is a member of this set is to call {@link Class#isPrimitive}.
+   *
+   * @since 3.0
+   */
+  public static Set<Class<?>> allPrimitiveTypes() {
+    return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
+  }
+
+  /**
+   * Returns an immutable set of all nine primitive-wrapper types (including
+   * {@link Void}).
+   *
+   * @since 3.0
+   */
+  public static Set<Class<?>> allWrapperTypes() {
+    return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
+  }
+
+  /**
+   * Returns {@code true} if {@code type} is one of the nine
+   * primitive-wrapper types, such as {@link Integer}.
+   *
+   * @see Class#isPrimitive
+   */
+  public static boolean isWrapperType(Class<?> type) {
+    return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(checkNotNull(type));
+  }
+
+  /**
+   * Returns the corresponding wrapper type of {@code type} if it is a primitive
+   * type; otherwise returns {@code type} itself. Idempotent.
+   * <pre>
+   *     wrap(int.class) == Integer.class
+   *     wrap(Integer.class) == Integer.class
+   *     wrap(String.class) == String.class
+   * </pre>
+   */
+  public static <T> Class<T> wrap(Class<T> type) {
+    checkNotNull(type);
+
+    // cast is safe: long.class and Long.class are both of type Class<Long>
+    @SuppressWarnings("unchecked")
+    Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(type);
+    return (wrapped == null) ? type : wrapped;
+  }
+
+  /**
+   * Returns the corresponding primitive type of {@code type} if it is a
+   * wrapper type; otherwise returns {@code type} itself. Idempotent.
+   * <pre>
+   *     unwrap(Integer.class) == int.class
+   *     unwrap(int.class) == int.class
+   *     unwrap(String.class) == String.class
+   * </pre>
+   */
+  public static <T> Class<T> unwrap(Class<T> type) {
+    checkNotNull(type);
+
+    // cast is safe: long.class and Long.class are both of type Class<Long>
+    @SuppressWarnings("unchecked")
+    Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(type);
+    return (unwrapped == null) ? type : unwrapped;
+  }
+}