org.apache.lucene.search.DoubleValues.java Source code

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Here is the source code for org.apache.lucene.search.DoubleValues.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.lucene.search;

import java.io.IOException;

/**
 * Per-segment, per-document double values, which can be calculated at search-time
 */
public abstract class DoubleValues {

    /**
     * Get the double value for the current document
     */
    public abstract double doubleValue() throws IOException;

    /**
     * Advance this instance to the given document id
     * @return true if there is a value for this document
     */
    public abstract boolean advanceExact(int doc) throws IOException;

    /**
     * Wrap a DoubleValues instance, returning a default if the wrapped instance has no value
     */
    public static DoubleValues withDefault(DoubleValues in, double missingValue) {
        return new DoubleValues() {

            boolean hasValue = false;

            @Override
            public double doubleValue() throws IOException {
                return hasValue ? in.doubleValue() : missingValue;
            }

            @Override
            public boolean advanceExact(int doc) throws IOException {
                hasValue = in.advanceExact(doc);
                return true;
            }
        };
    }

    /**
     * An empty DoubleValues instance that always returns {@code false} from {@link #advanceExact(int)}
     */
    public static final DoubleValues EMPTY = new DoubleValues() {
        @Override
        public double doubleValue() throws IOException {
            throw new UnsupportedOperationException();
        }

        @Override
        public boolean advanceExact(int doc) throws IOException {
            return false;
        }
    };

}