69 lines
2.0 KiB
Java
69 lines
2.0 KiB
Java
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/*
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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.base;
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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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/**
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* This class provides default values for all Java types, as defined by the JLS.
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*
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* @author Ben Yu
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* @since 1.0
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*/
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public final class Defaults {
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private Defaults() {
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}
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private static final Map<Class<?>, Object> DEFAULTS;
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static {
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// Only add to this map via put(Map, Class<T>, T)
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Map<Class<?>, Object> map = new HashMap<Class<?>, Object>();
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put(map, boolean.class, false);
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put(map, char.class, '\0');
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put(map, byte.class, (byte) 0);
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put(map, short.class, (short) 0);
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put(map, int.class, 0);
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put(map, long.class, 0L);
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put(map, float.class, 0f);
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put(map, double.class, 0d);
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DEFAULTS = Collections.unmodifiableMap(map);
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}
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private static <T> void put(Map<Class<?>, Object> map, Class<T> type, T value) {
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map.put(type, value);
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}
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/**
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* Returns the default value of {@code type} as defined by JLS --- {@code 0} for
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* numbers, {@code
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* false} for {@code boolean} and {@code '\0'} for {@code char}. For
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* non-primitive types and {@code void}, null is returned.
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*/
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public static <T> T defaultValue(Class<T> type) {
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// Primitives.wrap(type).cast(...) would avoid the warning, but we can't use
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// that from here
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@SuppressWarnings("unchecked") // the put method enforces this key-value relationship
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T t = (T) DEFAULTS.get(checkNotNull(type));
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return t;
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}
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}
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