001    /*
002     * Copyright (C) 2007 Google Inc.
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    
015    package com.google.common.base;
016    
017    import java.util.Collections;
018    import java.util.HashMap;
019    import java.util.Map;
020    
021    /**
022     * This class provides default values for all Java types, as defined by the JLS.
023     *
024     * @author Ben Yu
025     */
026    public final class Defaults {
027      private Defaults() {}
028    
029      private static final Map<Class<?>, Object> DEFAULTS;
030    
031      static {
032        Map<Class<?>, Object> map = new HashMap<Class<?>, Object>();
033        put(map, boolean.class, false);
034        put(map, char.class, '\0');
035        put(map, byte.class, (byte) 0);
036        put(map, short.class, (short) 0);
037        put(map, int.class, 0);
038        put(map, long.class, 0L);
039        put(map, float.class, 0f);
040        put(map, double.class, 0d);
041        DEFAULTS = Collections.unmodifiableMap(map);
042      }
043    
044      private static <T> void put(Map<Class<?>, Object> map, Class<T> type, T value) {
045        map.put(type, value);
046      }
047    
048      /**
049       * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
050       * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
051       * {@code void}, null is returned.
052       */
053      @SuppressWarnings("unchecked")
054      public static <T> T defaultValue(Class<T> type) {
055        return (T) DEFAULTS.get(type);
056      }
057    }