gson/com/google/gson/internal/Primitives.java

   1 /*
   2  * Copyright (C) 2008 Google Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 package com.google.gson.internal;
  18
  19
  20 import java.lang.reflect.Type;
  21 import java.util.Collections;
  22 import java.util.HashMap;
  23 import java.util.Map;
  24
  25 /**
  26  * Contains static utility methods pertaining to primitive types and their
  27  * corresponding wrapper types.
  28  *
  29  * @author Kevin Bourrillion
  30  */
  31 public final class Primitives {
  32   private Primitives() {}
  33
  34   /** A map from primitive types to their corresponding wrapper types. */
  35   private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;
  36
  37   /** A map from wrapper types to their corresponding primitive types. */
  38   private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;
  39
  40   // Sad that we can't use a BiMap. :(
  41
  42   static {
  43     Map<Class<?>, Class<?>> primToWrap = new HashMap<Class<?>, Class<?>>(16);
  44     Map<Class<?>, Class<?>> wrapToPrim = new HashMap<Class<?>, Class<?>>(16);
  45
  46     add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
  47     add(primToWrap, wrapToPrim, byte.class, Byte.class);
  48     add(primToWrap, wrapToPrim, char.class, Character.class);
  49     add(primToWrap, wrapToPrim, double.class, Double.class);
  50     add(primToWrap, wrapToPrim, float.class, Float.class);
  51     add(primToWrap, wrapToPrim, int.class, Integer.class);
  52     add(primToWrap, wrapToPrim, long.class, Long.class);
  53     add(primToWrap, wrapToPrim, short.class, Short.class);
  54     add(primToWrap, wrapToPrim, void.class, Void.class);
  55
  56     PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
  57     WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
  58   }
  59
  60   private static void add(Map<Class<?>, Class<?>> forward,
  61       Map<Class<?>, Class<?>> backward, Class<?> key, Class<?> value) {
  62     forward.put(key, value);
  63     backward.put(value, key);
  64   }
  65
  66   /**
  67    * Returns true if this type is a primitive.
  68    */
  69   public static boolean isPrimitive(Type type) {
  70     return PRIMITIVE_TO_WRAPPER_TYPE.containsKey(type);
  71   }
  72
  73   /**
  74    * Returns {@code true} if {@code type} is one of the nine
  75    * primitive-wrapper types, such as {@link Integer}.
  76    *
  77    * @see Class#isPrimitive
  78    */
  79   public static boolean isWrapperType(Type type) {
  80     return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(
  81         $Gson$Preconditions.checkNotNull(type));
  82   }
  83
  84   /**
  85    * Returns the corresponding wrapper type of {@code type} if it is a primitive
  86    * type; otherwise returns {@code type} itself. Idempotent.
  87    * <pre>
  88    *     wrap(int.class) == Integer.class
  89    *     wrap(Integer.class) == Integer.class
  90    *     wrap(String.class) == String.class
  91    * </pre>
  92    */
  93   public static <T> Class<T> wrap(Class<T> type) {
  94     // cast is safe: long.class and Long.class are both of type Class<Long>
  95     @SuppressWarnings("unchecked")
  96     Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(
  97         $Gson$Preconditions.checkNotNull(type));
  98     return (wrapped == null) ? type : wrapped;
  99   }
 100
 101   /**
 102    * Returns the corresponding primitive type of {@code type} if it is a
 103    * wrapper type; otherwise returns {@code type} itself. Idempotent.
 104    * <pre>
 105    *     unwrap(Integer.class) == int.class
 106    *     unwrap(int.class) == int.class
 107    *     unwrap(String.class) == String.class
 108    * </pre>
 109    */
 110   public static <T> Class<T> unwrap(Class<T> type) {
 111     // cast is safe: long.class and Long.class are both of type Class<Long>
 112     @SuppressWarnings("unchecked")
 113     Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(
 114         $Gson$Preconditions.checkNotNull(type));
 115     return (unwrapped == null) ? type : unwrapped;
 116   }
 117 }