Java Checksum Calculate checksum(InputStream is)

Description

Compute a checksum for the file or directory that consists of the name, length and the last modified date for a file and its children in case of a directory

License

Apache License

Parameter

Parameter	Description
is	the input stream

Return

a checksum identifying any change

Declaration

public static long checksum(InputStream is) throws IOException

Method Source Code

//package com.java2s;
/**/*from  www  .j  ava  2s  . com*/
 *  Copyright 2005-2014 Red Hat, Inc.
 *
 *  Red Hat 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.
 */

import java.io.*;

import java.util.zip.CRC32;

public class Main {
    /**
     * Compute a checksum for the file or directory that consists of the name, length and the last modified date
     * for a file and its children in case of a directory
     *
     * @param is the input stream
     * @return a checksum identifying any change
     */
    public static long checksum(InputStream is) throws IOException {
        try {
            CRC32 crc = new CRC32();
            byte[] buffer = new byte[8192];
            int l;
            while ((l = is.read(buffer)) > 0) {
                crc.update(buffer, 0, l);
            }
            return crc.getValue();
        } finally {
            if (is != null) {
                try {
                    is.close();
                } catch (IOException e) {
                    // Ignore
                }
            }
        }
    }
}