android/guava/src/com/google/common/base/Defaults.java

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.base;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;

/**
 * This class provides default values for all Java types, as defined by the JLS.
 *
 * @author Ben Yu
 * @since 1.0
 */
@GwtIncompatible
public final class Defaults {
  private Defaults() {}

  private static final Double DOUBLE_DEFAULT = Double.valueOf(0d);
  private static final Float FLOAT_DEFAULT = Float.valueOf(0f);

  /**
   * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
   * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
   * {@code void}, {@code null} is returned.
   */
  @SuppressWarnings("unchecked")
  @NullableDecl
  public static <T> T defaultValue(Class<T> type) {
    checkNotNull(type);
    if (type == boolean.class) {
      return (T) Boolean.FALSE;
    } else if (type == char.class) {
      return (T) Character.valueOf('\0');
    } else if (type == byte.class) {
      return (T) Byte.valueOf((byte) 0);
    } else if (type == short.class) {
      return (T) Short.valueOf((short) 0);
    } else if (type == int.class) {
      return (T) Integer.valueOf(0);
    } else if (type == long.class) {
      return (T) Long.valueOf(0L);
    } else if (type == float.class) {
      return (T) FLOAT_DEFAULT;
    } else if (type == double.class) {
      return (T) DOUBLE_DEFAULT;
    } else {
      return null;
    }
  }
}