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The Apache Commons CSV library provides a simple interface for reading and writing CSV files of various types.
There is a newer version: 1.2.2.1-jre17
/*
 * 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.csv;

import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.nio.CharBuffer;

/** Copied from Apache Commons IO. */
class IOUtils {

    /**
     * 
     * Copied from Apache Commons IO.
     * 
     * The default buffer size ({@value}).
     */
    static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * 
     * Copied from Apache Commons IO.
     * 
     * Represents the end-of-file (or stream).
     * @since 2.5 (made public)
     */
    private static final int EOF = -1;

    /**
     * Copies chars from a large (over 2GB) {@code Reader} to an {@code Appendable}.
     * 
     * This method buffers the input internally, so there is no need to use a
     * {@code BufferedReader}.
     * 
     * The buffer size is given by {@link #DEFAULT_BUFFER_SIZE}.
     *
     * @param input the {@code Reader} to read from
     * @param output the {@code Appendable} to append to
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 2.7
     */
    static long copy(final Reader input, final Appendable output) throws IOException {
        return copy(input, output, CharBuffer.allocate(DEFAULT_BUFFER_SIZE));
    }

    /**
     * Copies chars from a large (over 2GB) {@code Reader} to an {@code Appendable}.
     * 
     * This method uses the provided buffer, so there is no need to use a
     * {@code BufferedReader}.
     * 
     *
     * @param input the {@code Reader} to read from
     * @param output the {@code Appendable} to write to
     * @param buffer the buffer to be used for the copy
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 2.7
     */
    static long copy(final Reader input, final Appendable output, final CharBuffer buffer) throws IOException {
        long count = 0;
        int n;
        while (EOF != (n = input.read(buffer))) {
            buffer.flip();
            output.append(buffer, 0, n);
            count += n;
        }
        return count;
    }

    /**
     * 
     * Copied from Apache Commons IO.
     * 
     * Copies chars from a large (over 2GB) {@code Reader} to a {@code Writer}.
     * 
     * This method buffers the input internally, so there is no need to use a
     * {@code BufferedReader}.
     * 

     * The buffer size is given by {@link #DEFAULT_BUFFER_SIZE}.
     *
     * @param input the {@code Reader} to read from
     * @param output the {@code Writer} to write to
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 1.3
     */
    static long copyLarge(final Reader input, final Writer output) throws IOException {
        return copyLarge(input, output, new char[DEFAULT_BUFFER_SIZE]);
    }

    /**
     * 

     * Copied from Apache Commons IO.
     * 
     * Copies chars from a large (over 2GB) {@code Reader} to a {@code Writer}.
     * 
     * This method uses the provided buffer, so there is no need to use a
     * {@code BufferedReader}.
     * 
     *
     * @param input the {@code Reader} to read from
     * @param output the {@code Writer} to write to
     * @param buffer the buffer to be used for the copy
     * @return the number of characters copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 2.2
     */
    static long copyLarge(final Reader input, final Writer output, final char[] buffer) throws IOException {
        long count = 0;
        int n;
        while (EOF != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return count;
    }

}