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// Copyright (C) 2019 The Android Open Source Project
//
// 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.gerrit.index.query;

import static java.util.Objects.requireNonNull;

import com.google.common.collect.ImmutableList;
import java.util.Iterator;
import java.util.function.Supplier;

/**
 * Result set that allows for asynchronous execution of the actual query. Callers should dispatch
 * the query and call the constructor of this class with a supplier that fetches the result and
 * blocks on it if necessary.
 *
 * 

If the execution is synchronous or the results are known a priori, consider using {@link * ListResultSet}. */ public class LazyResultSet implements ResultSet { private final Supplier> resultsCallback; private boolean resultsReturned = false; public LazyResultSet(Supplier> r) { resultsCallback = requireNonNull(r, "results can't be null"); } @Override public Iterator iterator() { return toList().iterator(); } @Override public ImmutableList toList() { if (resultsReturned) { throw new IllegalStateException("Results already obtained"); } resultsReturned = true; return resultsCallback.get(); } @Override public void close() {} @Override public Object searchAfter() { return null; } }





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