138 lines
4.3 KiB
Java
138 lines
4.3 KiB
Java
/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.primitives;
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import static com.google.common.base.Preconditions.checkNotNull;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Set;
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/**
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* Contains static utility methods pertaining to primitive types and their
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* corresponding wrapper types.
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*
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* @author Kevin Bourrillion
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* @since 1.0
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*/
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public final class Primitives {
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private Primitives() {
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}
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/** A map from primitive types to their corresponding wrapper types. */
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private static final Map<Class<?>, Class<?>> PRIMITIVE_TO_WRAPPER_TYPE;
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/** A map from wrapper types to their corresponding primitive types. */
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private static final Map<Class<?>, Class<?>> WRAPPER_TO_PRIMITIVE_TYPE;
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// Sad that we can't use a BiMap. :(
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static {
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Map<Class<?>, Class<?>> primToWrap = new HashMap<Class<?>, Class<?>>(16);
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Map<Class<?>, Class<?>> wrapToPrim = new HashMap<Class<?>, Class<?>>(16);
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add(primToWrap, wrapToPrim, boolean.class, Boolean.class);
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add(primToWrap, wrapToPrim, byte.class, Byte.class);
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add(primToWrap, wrapToPrim, char.class, Character.class);
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add(primToWrap, wrapToPrim, double.class, Double.class);
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add(primToWrap, wrapToPrim, float.class, Float.class);
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add(primToWrap, wrapToPrim, int.class, Integer.class);
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add(primToWrap, wrapToPrim, long.class, Long.class);
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add(primToWrap, wrapToPrim, short.class, Short.class);
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add(primToWrap, wrapToPrim, void.class, Void.class);
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PRIMITIVE_TO_WRAPPER_TYPE = Collections.unmodifiableMap(primToWrap);
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WRAPPER_TO_PRIMITIVE_TYPE = Collections.unmodifiableMap(wrapToPrim);
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}
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private static void add(Map<Class<?>, Class<?>> forward, Map<Class<?>, Class<?>> backward, Class<?> key,
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Class<?> value) {
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forward.put(key, value);
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backward.put(value, key);
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}
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/**
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* Returns an immutable set of all nine primitive types (including {@code
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* void}). Note that a simpler way to test whether a {@code Class} instance is a
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* member of this set is to call {@link Class#isPrimitive}.
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*
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* @since 3.0
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*/
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public static Set<Class<?>> allPrimitiveTypes() {
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return PRIMITIVE_TO_WRAPPER_TYPE.keySet();
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}
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/**
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* Returns an immutable set of all nine primitive-wrapper types (including
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* {@link Void}).
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*
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* @since 3.0
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*/
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public static Set<Class<?>> allWrapperTypes() {
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return WRAPPER_TO_PRIMITIVE_TYPE.keySet();
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}
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/**
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* Returns {@code true} if {@code type} is one of the nine primitive-wrapper
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* types, such as {@link Integer}.
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*
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* @see Class#isPrimitive
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*/
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public static boolean isWrapperType(Class<?> type) {
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return WRAPPER_TO_PRIMITIVE_TYPE.containsKey(checkNotNull(type));
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}
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/**
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* Returns the corresponding wrapper type of {@code type} if it is a primitive
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* type; otherwise returns {@code type} itself. Idempotent.
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*
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* <pre>
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* wrap(int.class) == Integer.class
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* wrap(Integer.class) == Integer.class
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* wrap(String.class) == String.class
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* </pre>
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*/
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public static <T> Class<T> wrap(Class<T> type) {
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checkNotNull(type);
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// cast is safe: long.class and Long.class are both of type Class<Long>
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@SuppressWarnings("unchecked")
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Class<T> wrapped = (Class<T>) PRIMITIVE_TO_WRAPPER_TYPE.get(type);
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return (wrapped == null) ? type : wrapped;
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}
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/**
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* Returns the corresponding primitive type of {@code type} if it is a wrapper
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* type; otherwise returns {@code type} itself. Idempotent.
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*
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* <pre>
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* unwrap(Integer.class) == int.class
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* unwrap(int.class) == int.class
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* unwrap(String.class) == String.class
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* </pre>
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*/
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public static <T> Class<T> unwrap(Class<T> type) {
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checkNotNull(type);
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// cast is safe: long.class and Long.class are both of type Class<Long>
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@SuppressWarnings("unchecked")
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Class<T> unwrapped = (Class<T>) WRAPPER_TO_PRIMITIVE_TYPE.get(type);
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return (unwrapped == null) ? type : unwrapped;
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}
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}
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