@Override
  public int hashCode() {
    return delegate.hashCode();
  }

  private void validate() {
    // Don't use checkState(), because we don't want the overhead of generating the error message
    // unless it's actually going to be used; validate() is called for all set method calls, so it
    // needs to be fast.
    // (We could instead generate the message once, when the set is created, but zero is better.)

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 * You may obtain a copy of the License at
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 * Unless required by applicable law or agreed to in writing, software
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 * with the License.  You may obtain a copy of the License at
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 * Unless required by applicable law or agreed to in writing,
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 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
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 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
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 * KIND, either express or implied.  See the License for the