new ByteSource() {
          @Override
          public InputStream openStream() throws IOException {
            if (counter[0]++ != 0) {
              throw new IllegalStateException("More than one source open");
            }
            return new FilterInputStream(source.openStream()) {
              @Override
              public void close() throws IOException {
                super.close();

 * future version of {@code com.google.common.base.Supplier} will be made to <i>extend</i> {@code
 * java.util.function.Supplier}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Harry Heymann
 * @since 2.0
 */
@GwtCompatible
public interface Supplier<T extends @Nullable Object> {
  /**

import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutionException;
import org.jspecify.annotations.Nullable;

/**
 * A cache which forwards all its method calls to another cache. Subclasses should override one or
 * more methods to modify the behavior of the backing cache as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * @author Charles Fry
 * @since 10.0
 */

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *

  private void checkCurrentState(State expected) {
    State actual = state();
    if (actual != expected) {
      if (actual == FAILED) {
        // Handle this specially so that we can include the failureCause, if there is one.
        throw new IllegalStateException(
            "Expected the service " + this + " to be " + expected + ", but the service has FAILED",
            failureCause());
      }
      throw new IllegalStateException(

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
 *

##
## Licensed to the Apache Software Foundation (ASF) under one
## or more contributor license agreements.  See the NOTICE file
## distributed with this work for additional information
## regarding copyright ownership.  The ASF licenses this file
## to you 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
##