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.CheckForNull;
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
029@ElementTypesAreNonnullByDefault
030public final class Defaults {
031  private Defaults() {}
032
033  private static final Double DOUBLE_DEFAULT = 0d;
034  private static final Float FLOAT_DEFAULT = 0f;
035
036  /**
037   * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
038   * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
039   * {@code void}, {@code null} is returned.
040   */
041  @SuppressWarnings("unchecked")
042  @CheckForNull
043  public static <T> T defaultValue(Class<T> type) {
044    checkNotNull(type);
045    if (type.isPrimitive()) {
046      if (type == boolean.class) {
047        return (T) Boolean.FALSE;
048      } else if (type == char.class) {
049        return (T) Character.valueOf('\0');
050      } else if (type == byte.class) {
051        return (T) Byte.valueOf((byte) 0);
052      } else if (type == short.class) {
053        return (T) Short.valueOf((short) 0);
054      } else if (type == int.class) {
055        return (T) Integer.valueOf(0);
056      } else if (type == long.class) {
057        return (T) Long.valueOf(0L);
058      } else if (type == float.class) {
059        return (T) FLOAT_DEFAULT;
060      } else if (type == double.class) {
061        return (T) DOUBLE_DEFAULT;
062      }
063    }
064    return null;
065  }
066}