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 com.google.common.annotations.GwtCompatible;
018import org.jspecify.annotations.Nullable;
019
020/**
021 * Legacy version of {@link java.util.function.Supplier java.util.function.Supplier}. Semantically,
022 * this could be a factory, generator, builder, closure, or something else entirely. No guarantees
023 * are implied by this interface.
024 *
025 * <p>The {@link Suppliers} class provides common suppliers and related utilities.
026 *
027 * <p>As this interface extends {@code java.util.function.Supplier}, an instance of this type can be
028 * used as a {@code java.util.function.Supplier} directly. To use a {@code
029 * java.util.function.Supplier} in a context where a {@code com.google.common.base.Supplier} is
030 * needed, use {@code supplier::get}.
031 *
032 * <p>See the Guava User Guide article on <a
033 * href="https://github.com/google/guava/wiki/FunctionalExplained">the use of {@code Function}</a>.
034 *
035 * @author Harry Heymann
036 * @since 2.0
037 */
038@GwtCompatible
039@FunctionalInterface
040public interface Supplier<T extends @Nullable Object> extends java.util.function.Supplier<T> {
041  /**
042   * Retrieves an instance of the appropriate type. The returned object may or may not be a new
043   * instance, depending on the implementation.
044   *
045   * @return an instance of the appropriate type
046   */
047  @Override
048  @ParametricNullness
049  T get();
050
051  /**
052   * <i>May</i> return {@code true} if {@code object} is a {@code Supplier} that behaves identically
053   * to this supplier.
054   *
055   * <p><b>Warning: do not depend</b> on the behavior of this method.
056   *
057   * <p>Historically, {@code Supplier} instances in this library have implemented this method to
058   * recognize certain cases where distinct {@code Supplier} instances would in fact behave
059   * identically. However, as code migrates to {@code java.util.function}, that behavior will
060   * disappear. It is best not to depend on it.
061   */
062  @Override
063  boolean equals(@Nullable Object object);
064}