001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.primitives; 016 017import static com.google.common.base.Preconditions.checkNotNull; 018 019import com.google.common.annotations.GwtIncompatible; 020import java.util.Collections; 021import java.util.HashMap; 022import java.util.Map; 023import java.util.Set; 024 025/** 026 * Contains static utility methods pertaining to primitive types and their corresponding wrapper 027 * types. 028 * 029 * @author Kevin Bourrillion 030 * @since 1.0 031 */ 032@GwtIncompatible 033public 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( 063 Map<Class<?>, Class<?>> forward, 064 Map<Class<?>, Class<?>> backward, 065 Class<?> key, 066 Class<?> value) { 067 forward.put(key, value); 068 backward.put(value, key); 069 } 070 071 /** 072 * Returns an immutable set of all nine primitive types (including {@code 073 * void}). Note that a simpler way to test whether a {@code Class} instance is a member of this 074 * set is to call {@link Class#isPrimitive}. 075 * 076 * @since 3.0 077 */ 078 public static Set<Class<?>> allPrimitiveTypes() { 079 return PRIMITIVE_TO_WRAPPER_TYPE.keySet(); 080 } 081 082 /** 083 * Returns an immutable set of all nine primitive-wrapper types (including {@link Void}). 084 * 085 * @since 3.0 086 */ 087 public static Set<Class<?>> allWrapperTypes() { 088 return WRAPPER_TO_PRIMITIVE_TYPE.keySet(); 089 } 090 091 /** 092 * Returns {@code true} if {@code type} is one of the nine primitive-wrapper types, such as 093 * {@link Integer}. 094 * 095 * @see Class#isPrimitive 096 */ 097 public static boolean isWrapperType(Class<?> type) { 098 return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(checkNotNull(type)); 099 } 100 101 /** 102 * Returns the corresponding wrapper type of {@code type} if it is a primitive type; otherwise 103 * returns {@code type} itself. Idempotent. 104 * 105 * <pre> 106 * wrap(int.class) == Integer.class 107 * wrap(Integer.class) == Integer.class 108 * wrap(String.class) == String.class 109 * </pre> 110 */ 111 public static <T> Class<T> wrap(Class<T> type) { 112 checkNotNull(type); 113 114 // cast is safe: long.class and Long.class are both of type Class<Long> 115 @SuppressWarnings("unchecked") 116 Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(type); 117 return (wrapped == null) ? type : wrapped; 118 } 119 120 /** 121 * Returns the corresponding primitive type of {@code type} if it is a wrapper type; otherwise 122 * returns {@code type} itself. Idempotent. 123 * 124 * <pre> 125 * unwrap(Integer.class) == int.class 126 * unwrap(int.class) == int.class 127 * unwrap(String.class) == String.class 128 * </pre> 129 */ 130 public static <T> Class<T> unwrap(Class<T> type) { 131 checkNotNull(type); 132 133 // cast is safe: long.class and Long.class are both of type Class<Long> 134 @SuppressWarnings("unchecked") 135 Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(type); 136 return (unwrapped == null) ? type : unwrapped; 137 } 138}