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.base;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.annotations.GwtIncompatible;
020import javax.annotation.Nullable;
021
022/**
023 * This class provides default values for all Java types, as defined by the JLS.
024 *
025 * @author Ben Yu
026 * @since 1.0
027 */
028@GwtIncompatible
029public final class Defaults {
030  private Defaults() {}
031
032  private static final Double DOUBLE_DEFAULT = Double.valueOf(0d);
033  private static final Float FLOAT_DEFAULT = Float.valueOf(0f);
034
035  /**
036   * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
037   * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
038   * {@code void}, {@code null} is returned.
039   */
040  @Nullable
041  @SuppressWarnings("unchecked")
042  public static <T> T defaultValue(Class<T> type) {
043    checkNotNull(type);
044    if (type == boolean.class) {
045      return (T) Boolean.FALSE;
046    } else if (type == char.class) {
047      return (T) Character.valueOf('\0');
048    } else if (type == byte.class) {
049      return (T) Byte.valueOf((byte) 0);
050    } else if (type == short.class) {
051      return (T) Short.valueOf((short) 0);
052    } else if (type == int.class) {
053      return (T) Integer.valueOf(0);
054    } else if (type == long.class) {
055      return (T) Long.valueOf(0L);
056    } else if (type == float.class) {
057      return (T) FLOAT_DEFAULT;
058    } else if (type == double.class) {
059      return (T) DOUBLE_DEFAULT;
060    } else {
061      return null;
062    }
063  }
064}