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/*
* 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;
}
}
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