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The Apache Commons IO library contains utility classes, stream implementations, file filters, file comparators, endian transformation classes, and much more.

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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.commons.io.input;

import java.io.Reader;
import java.util.Collections;
import java.util.Set;

/**
 * A filter reader that removes a given set of characters represented as int code points, handy to remove
 * known junk characters from CSV files for example.
 * 
 * This class must convert each int read to an Integer. You can increase the Integer cache
 * with a system property, see {@link Integer}.
 * 
 */
public class CharacterSetFilterReader extends AbstractCharacterFilterReader {

    private static final Set EMPTY_SET = Collections.emptySet();
    private final Set skipSet;

    /**
     * Constructs a new reader.
     *
     * @param reader
     *            the reader to filter.
     * @param skip
     *            the set of characters to filter out.
     */
    public CharacterSetFilterReader(final Reader reader, final Set skip) {
        super(reader);
        this.skipSet = skip == null ? EMPTY_SET : Collections.unmodifiableSet(skip);
    }

    @Override
    protected boolean filter(final int ch) {
        // Note WRT Integer.valueOf(): You can increase the Integer cache with a system property, see {@link Integer}.
        return skipSet.contains(Integer.valueOf(ch));
    }

}