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 com.google.common.annotations.J2ktIncompatible;
021import org.jspecify.annotations.Nullable;
022
023/**
024 * This class provides default values for all Java types, as defined by the JLS.
025 *
026 * @author Ben Yu
027 * @since 1.0
028 */
029@J2ktIncompatible
030@GwtIncompatible
031public final class Defaults {
032  private Defaults() {}
033
034  private static final Double DOUBLE_DEFAULT = 0d;
035  private static final Float FLOAT_DEFAULT = 0f;
036
037  /**
038   * Returns the default value of {@code type} as defined by JLS --- {@code 0} for numbers, {@code
039   * false} for {@code boolean} and {@code '\0'} for {@code char}. For non-primitive types and
040   * {@code void}, {@code null} is returned.
041   */
042  @SuppressWarnings({
043    /*
044     * `type.cast(...)` would be wrong because `type` is a primitive. We'd need
045     * `c.g.c.primitives.Primitives.wrap(type).cast(...)`, and we can't depend on `primitives` from
046     * `base`.
047     */
048    "unchecked",
049    "BooleanLiteral" // `(T) false` would produce an error
050  })
051  public static <T> @Nullable T defaultValue(Class<T> type) {
052    checkNotNull(type);
053    if (type.isPrimitive()) {
054      if (type == boolean.class) {
055        return (T) Boolean.FALSE;
056      } else if (type == char.class) {
057        return (T) Character.valueOf('\0');
058      } else if (type == byte.class) {
059        return (T) Byte.valueOf((byte) 0);
060      } else if (type == short.class) {
061        return (T) Short.valueOf((short) 0);
062      } else if (type == int.class) {
063        return (T) Integer.valueOf(0);
064      } else if (type == long.class) {
065        return (T) Long.valueOf(0L);
066      } else if (type == float.class) {
067        return (T) FLOAT_DEFAULT;
068      } else if (type == double.class) {
069        return (T) DOUBLE_DEFAULT;
070      }
071    }
072    return null;
073  }
074}