1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.base;
18
19import java.util.Collections;
20import java.util.HashMap;
21import java.util.Map;
22
23/**
24 * This class provides default values for all Java types, as defined by the JLS.
25 *
26 * @author Ben Yu
27 */
28public final class Defaults {
29  private Defaults() {}
30
31  private static final Map<Class<?>, Object> DEFAULTS;
32
33  static {
34    Map<Class<?>, Object> map = new HashMap<Class<?>, Object>();
35    put(map, boolean.class, false);
36    put(map, char.class, '\0');
37    put(map, byte.class, (byte) 0);
38    put(map, short.class, (short) 0);
39    put(map, int.class, 0);
40    put(map, long.class, 0L);
41    put(map, float.class, 0f);
42    put(map, double.class, 0d);
43    DEFAULTS = Collections.unmodifiableMap(map);
44  }
45
46  private static <T> void put(Map<Class<?>, Object> map, Class<T> type, T value) {
47    map.put(type, value);
48  }
49
50  /**
51   * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
52   * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
53   * {@code void}, null is returned.
54   */
55  @SuppressWarnings("unchecked")
56  public static <T> T defaultValue(Class<T> type) {
57    return (T) DEFAULTS.get(type);
58  }
59}
60