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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);
}
}