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/*
 * Copyright 2007 Kasper B. Graversen
 * 
 * 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 org.supercsv.cellprocessor.constraint;

import java.util.HashSet;
import java.util.Set;

import org.supercsv.cellprocessor.CellProcessorAdaptor;
import org.supercsv.cellprocessor.ift.CellProcessor;
import org.supercsv.exception.SuperCsvCellProcessorException;
import org.supercsv.exception.SuperCsvConstraintViolationException;
import org.supercsv.util.CsvContext;

/**
 * Ensure that upon processing a CSV file (reading or writing), that values of the column are all unique. Comparison is
 * based upon each elements hashCode() method and lookup takes O(1).
 * 

* Compared to {@link Unique} this processor is much more memory efficient as it only stores the set of encountered * hashcodes rather than storing references to all encountered objects. The tradeoff being possible false positives. *

* Prior to v1.50 this class was named Unique but has been renamed to clarify its inner workings. * * @author Kasper B. Graversen * @author Dominique De Vito * @author James Bassett */ public class UniqueHashCode extends CellProcessorAdaptor { private final Set uniqueSet = new HashSet(); /** * Constructs a new UniqueHashCode processor, which ensures that all rows in a column are unique. */ public UniqueHashCode() { super(); } /** * Constructs a new UniqueHashCode processor, which ensures that all rows in a column are unique, then * calls the next processor in the chain. * * @param next * the next processor in the chain * @throws NullPointerException * if next is null */ public UniqueHashCode(final CellProcessor next) { super(next); } /** * {@inheritDoc} * * @throws SuperCsvCellProcessorException * if value is null * @throws SuperCsvConstraintViolationException * if a non-unique value is encountered */ public Object execute(final Object value, final CsvContext context) { validateInputNotNull(value, context); int hash = value.hashCode(); if( !uniqueSet.add(hash) ) { throw new SuperCsvConstraintViolationException( String.format("duplicate value '%s' encountered with hashcode %d", value, hash), context, this); } return next.execute(value, context); } }





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