A single checksum calculation for multiple files : Zip Tar File « File Input Output « Java

A single checksum calculation for multiple files

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 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.zip.Adler32;
import java.util.zip.CheckedInputStream;
import java.util.zip.Checksum;

 * Perform a single checksum calculation for multiple files
 * @author <a href="mailto:ate@douma.nu">Ate Douma</a>
 * @author <a href="mailto:taylor@apache.org">David Sean Taylor </a>
 * @version $Id$
public class MultiFileChecksumHelper
    public static long getChecksum(File[] files)
        CheckedInputStream cis = null;
        FileInputStream is = null;
        Checksum checksum = new Adler32();
        byte[] tempBuf = new byte[128];
        for ( int i = 0; i < files.length && files[i] != null && files[i].exists() && files[i].isFile(); i++ )
                is = new FileInputStream(files[i]);
                cis = new CheckedInputStream(is, checksum);
                while (cis.read(tempBuf) >= 0) {}                
            catch (Exception e)
                throw new RuntimeException(e);
                if (cis != null)
                    catch (IOException ioe) {}
                    cis = null;
                if (is != null)
                    catch (IOException ioe) {}
                    is = null;
        return checksum.getValue();


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