001 /*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package com.google.common.primitives;
018
019 import static com.google.common.base.Preconditions.checkNotNull;
020
021 import java.util.Collections;
022 import java.util.HashMap;
023 import java.util.Map;
024 import java.util.Set;
025
026 /**
027 * Contains static utility methods pertaining to primitive types and their
028 * corresponding wrapper types.
029 *
030 * @author Kevin Bourrillion
031 * @since 1.0
032 */
033 public final class Primitives {
034 private Primitives() {}
035
036 /** A map from primitive types to their corresponding wrapper types. */
037 private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;
038
039 /** A map from wrapper types to their corresponding primitive types. */
040 private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;
041
042 // Sad that we can't use a BiMap. :(
043
044 static {
045 Map<Class<?>, Class<?>> primToWrap = new HashMap<Class<?>, Class<?>>(16);
046 Map<Class<?>, Class<?>> wrapToPrim = new HashMap<Class<?>, Class<?>>(16);
047
048 add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
049 add(primToWrap, wrapToPrim, byte.class, Byte.class);
050 add(primToWrap, wrapToPrim, char.class, Character.class);
051 add(primToWrap, wrapToPrim, double.class, Double.class);
052 add(primToWrap, wrapToPrim, float.class, Float.class);
053 add(primToWrap, wrapToPrim, int.class, Integer.class);
054 add(primToWrap, wrapToPrim, long.class, Long.class);
055 add(primToWrap, wrapToPrim, short.class, Short.class);
056 add(primToWrap, wrapToPrim, void.class, Void.class);
057
058 PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
059 WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
060 }
061
062 private static void add(Map<Class<?>, Class<?>> forward,
063 Map<Class<?>, Class<?>> backward, Class<?> key, Class<?> value) {
064 forward.put(key, value);
065 backward.put(value, key);
066 }
067
068 /**
069 * Returns an immutable set of all nine primitive types (including {@code
070 * void}). Note that a simpler way to test whether a {@code Class} instance
071 * is a member of this set is to call {@link Class#isPrimitive}.
072 *
073 * @since 3.0
074 */
075 public static Set<Class<?>> allPrimitiveTypes() {
076 return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
077 }
078
079 /**
080 * Returns an immutable set of all nine primitive-wrapper types (including
081 * {@link Void}).
082 *
083 * @since 3.0
084 */
085 public static Set<Class<?>> allWrapperTypes() {
086 return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
087 }
088
089 /**
090 * Returns {@code true} if {@code type} is one of the nine
091 * primitive-wrapper types, such as {@link Integer}.
092 *
093 * @see Class#isPrimitive
094 */
095 public static boolean isWrapperType(Class<?> type) {
096 return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(checkNotNull(type));
097 }
098
099 /**
100 * Returns the corresponding wrapper type of {@code type} if it is a primitive
101 * type; otherwise returns {@code type} itself. Idempotent.
102 * <pre>
103 * wrap(int.class) == Integer.class
104 * wrap(Integer.class) == Integer.class
105 * wrap(String.class) == String.class
106 * </pre>
107 */
108 public static <T> Class<T> wrap(Class<T> type) {
109 checkNotNull(type);
110
111 // cast is safe: long.class and Long.class are both of type Class<Long>
112 @SuppressWarnings("unchecked")
113 Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(type);
114 return (wrapped == null) ? type : wrapped;
115 }
116
117 /**
118 * Returns the corresponding primitive type of {@code type} if it is a
119 * wrapper type; otherwise returns {@code type} itself. Idempotent.
120 * <pre>
121 * unwrap(Integer.class) == int.class
122 * unwrap(int.class) == int.class
123 * unwrap(String.class) == String.class
124 * </pre>
125 */
126 public static <T> Class<T> unwrap(Class<T> type) {
127 checkNotNull(type);
128
129 // cast is safe: long.class and Long.class are both of type Class<Long>
130 @SuppressWarnings("unchecked")
131 Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(type);
132 return (unwrapped == null) ? type : unwrapped;
133 }
134 }