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    • com.hazelcast.jet.impl.AutoCloseableTraversers Maven / Gradle / Ivy

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    /*
 * Copyright (c) 2008-2024, Hazelcast, Inc. All Rights Reserved.
 *
 * 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.hazelcast.jet.impl;

import com.hazelcast.jet.Traverser;
import com.hazelcast.jet.impl.util.AutoCloseableTraverser;

import javax.annotation.Nonnull;
import java.util.Iterator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;

import static java.util.Objects.requireNonNull;

public class AutoCloseableTraversers {

    private static final AutoCloseableTraverser EMPTY_AUTOCLOSEABLE_TRAVERSER = new EmptyAutoCloseableTraverser<>();

    private AutoCloseableTraversers() {
    }

    @SuppressWarnings("unchecked")
    @Nonnull
    public static  AutoCloseableTraverser emptyAutoCloseableTraverser() {
        return (AutoCloseableTraverser) EMPTY_AUTOCLOSEABLE_TRAVERSER;
    }

    /**
     * Returns an adapter from {@code Iterator} to {@code Traverser}. The
     * iterator must return non-{@code null} items. Each time its {@code next()}
     * method is called, the traverser will take another item from the iterator
     * and return it.
     */
    @Nonnull
    public static  AutoCloseableTraverser traverseAutoCloseableIterator(@Nonnull Iterator iterator) {
        return new AutoCloseableTraverser<>() {
            @Override
            public T next() {
                return iterator.hasNext() ? requireNonNull(iterator.next(), "Iterator returned a null item") : null;
            }

            @Override
            public void close() throws Exception {
                if (iterator instanceof AutoCloseable autoCloseable) {
                    autoCloseable.close();
                }
            }
        };
    }

    private static final class EmptyAutoCloseableTraverser implements AutoCloseableTraverser {
        @Override
        public T next() {
            return null;
        }

        @SuppressWarnings("unchecked")
        @Nonnull @Override
        public  Traverser map(@Nonnull Function mapFn) {
            return (Traverser) this;
        }

        @SuppressWarnings("unchecked")
        @Nonnull @Override
        public  Traverser flatMap(@Nonnull Function> flatMapFn) {
            return (Traverser) this;
        }

        @Nonnull @Override
        public Traverser filter(@Nonnull Predicate filterFn) {
            return this;
        }

        @Nonnull @Override
        public Traverser takeWhile(@Nonnull Predicate predicate) {
            return this;
        }

        @Nonnull @Override
        public Traverser dropWhile(@Nonnull Predicate predicate) {
            return this;
        }

        @Nonnull @Override
        public Traverser peek(@Nonnull Consumer action) {
            return this;
        }
    }
}
    
    
    
    

    




    
    
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