Line data    Source code

       1             : // Copyright 2008 Google Inc.
       2             : //
       3             : // Licensed under the Apache License, Version 2.0 (the "License");
       4             : // you may not use this file except in compliance with the License.
       5             : // You may obtain a copy of the License at
       6             : //
       7             : // http://www.apache.org/licenses/LICENSE-2.0
       8             : //
       9             : // Unless required by applicable law or agreed to in writing, software
      10             : // distributed under the License is distributed on an "AS IS" BASIS,
      11             : // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      12             : // See the License for the specific language governing permissions and
      13             : // limitations under the License.
      14             : 
      15             : package com.google.gerrit.index.query;
      16             : 
      17             : import static java.util.Objects.requireNonNull;
      18             : 
      19             : import com.google.common.collect.ImmutableList;
      20             : import java.util.Iterator;
      21             : import java.util.List;
      22             : 
      23             : /**
      24             :  * Result set for queries that run synchronously or for cases where the result is already known and
      25             :  * we just need to pipe it back through our interfaces.
      26             :  *
      27             :  * <p>If your implementation benefits from asynchronous execution (i.e. dispatching a query and
      28             :  * awaiting results only when {@link ResultSet#toList()} is called, consider using {@link
      29             :  * LazyResultSet}.
      30             :  */
      31             : public class ListResultSet<T> implements ResultSet<T> {
      32             :   private ImmutableList<T> results;
      33             : 
      34         151 :   public ListResultSet(List<T> r) {
      35         151 :     results = ImmutableList.copyOf(requireNonNull(r, "results can't be null"));
      36         151 :   }
      37             : 
      38             :   @Override
      39             :   public Iterator<T> iterator() {
      40         120 :     return toList().iterator();
      41             :   }
      42             : 
      43             :   @Override
      44             :   public ImmutableList<T> toList() {
      45         151 :     if (results == null) {
      46           0 :       throw new IllegalStateException("Results already obtained");
      47             :     }
      48         151 :     ImmutableList<T> r = results;
      49         151 :     results = null;
      50         151 :     return r;
      51             :   }
      52             : 
      53             :   @Override
      54             :   public void close() {
      55           0 :     results = null;
      56           0 :   }
      57             : 
      58             :   @Override
      59             :   public Object searchAfter() {
      60           0 :     return null;
      61             :   }
      62             : }