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Explore the source code of the class Primitives.java

/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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.gson.internal;


import java.lang.reflect.Type;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * Contains static utility methods pertaining to primitive types and their
 * corresponding wrapper types.
 *
 * @author Kevin Bourrillion
 */
public final class Primitives {
  private Primitives() {
    throw new UnsupportedOperationException();
  }

  /** A map from primitive types to their corresponding wrapper types. */
  private static final Map, Class> PRIMITIVE_TO_WRAPPER_TYPE;

  /** A map from wrapper types to their corresponding primitive types. */
  private static final Map, Class> WRAPPER_TO_PRIMITIVE_TYPE;

  // Sad that we can't use a BiMap. :(

  static {
    Map, Class> primToWrap = new HashMap, Class>(16);
    Map, Class> wrapToPrim = new HashMap, 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> forward,
      Map, Class> backward, Class key, Class value) {
    forward.put(key, value);
    backward.put(value, key);
  }

  /**
   * Returns true if this type is a primitive.
   */
  public static boolean isPrimitive(Type type) {
    return PRIMITIVE_TO_WRAPPER_TYPE.containsKey(type);
  }

  /**
   * Returns [email protected] true} if [email protected] type} is one of the nine
   * primitive-wrapper types, such as [email protected] Integer}.
   *
   * @see Class#isPrimitive
   */
  public static boolean isWrapperType(Type type) {
    return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(
        $Gson$Preconditions.checkNotNull(type));
  }

  /**
   * Returns the corresponding wrapper type of [email protected] type} if it is a primitive
   * type; otherwise returns [email protected] type} itself. Idempotent.
   * 
   *     wrap(int.class) == Integer.class
   *     wrap(Integer.class) == Integer.class
   *     wrap(String.class) == String.class
   * 
*/ public static Class wrap(Class type) { // cast is safe: long.class and Long.class are both of type Class @SuppressWarnings("unchecked") Class wrapped = (Class) PRIMITIVE_TO_WRAPPER_TYPE.get( $Gson$Preconditions.checkNotNull(type)); return (wrapped == null) ? type : wrapped; } /** * Returns the corresponding primitive type of [email protected] type} if it is a * wrapper type; otherwise returns [email protected] type} itself. Idempotent. *
   *     unwrap(Integer.class) == int.class
   *     unwrap(int.class) == int.class
   *     unwrap(String.class) == String.class
   * 
*/ public static Class unwrap(Class type) { // cast is safe: long.class and Long.class are both of type Class @SuppressWarnings("unchecked") Class unwrapped = (Class) WRAPPER_TO_PRIMITIVE_TYPE.get( $Gson$Preconditions.checkNotNull(type)); return (unwrapped == null) ? type : unwrapped; } }