| /* |
| * Copyright 2000-2014 JetBrains s.r.o. |
| * |
| * 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.intellij.util; |
| |
| import com.intellij.concurrency.AsyncFuture; |
| import com.intellij.concurrency.AsyncUtil; |
| import org.jetbrains.annotations.NotNull; |
| |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.Iterator; |
| |
| /** |
| * @author max |
| */ |
| public class EmptyQuery<R> implements Query<R> { |
| private static final EmptyQuery EMPTY_QUERY_INSTANCE = new EmptyQuery(); |
| |
| @Override |
| @NotNull |
| public Collection<R> findAll() { |
| return Collections.emptyList(); |
| } |
| |
| @Override |
| public R findFirst() { |
| return null; |
| } |
| |
| @Override |
| public boolean forEach(@NotNull Processor<R> consumer) { |
| return true; |
| } |
| |
| @NotNull |
| @Override |
| public AsyncFuture<Boolean> forEachAsync(@NotNull Processor<R> consumer) { |
| return AsyncUtil.wrapBoolean(true); |
| } |
| |
| @NotNull |
| @Override |
| public R[] toArray(@NotNull R[] a) { |
| return findAll().toArray(a); |
| } |
| |
| @Override |
| public Iterator<R> iterator() { |
| return findAll().iterator(); |
| } |
| |
| public static <T> Query<T> getEmptyQuery() { |
| @SuppressWarnings("unchecked") Query<T> instance = (Query<T>)EMPTY_QUERY_INSTANCE; |
| return instance; |
| } |
| } |