Java I/O How to - Compare the contents of two Streams to determine if they are equal or not

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Question

We would like to know how to compare the contents of two Streams to determine if they are equal or not.

Answer

/*from   ww w  .j  av a  2 s .  co  m*/
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
public class Main {

  public static boolean contentEquals(InputStream input1, InputStream input2) throws IOException
  {
    if (!(input1 instanceof BufferedInputStream))
    {
      input1 = new BufferedInputStream(input1);
    }
    if (!(input2 instanceof BufferedInputStream))
    {
      input2 = new BufferedInputStream(input2);
    }

    int ch = input1.read();
    while (-1 != ch)
    {
      int ch2 = input2.read();
      if (ch != ch2)
      {
        return false;
      }
      ch = input1.read();
    }

    int ch2 = input2.read();
    return (ch2 == -1);
  }
}

Another solution

//from   ww w  . j av  a 2s . c o m
/*
 * JBoss DNA (http://www.jboss.org/dna)
 * See the COPYRIGHT.txt file distributed with this work for information
 * regarding copyright ownership.  Some portions may be licensed
 * to Red Hat, Inc. under one or more contributor license agreements.
 * See the AUTHORS.txt file in the distribution for a full listing of 
 * individual contributors. 
 *
 * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA
 * is licensed to you under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * JBoss DNA is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.util.Arrays;
/**
 * @author Randall Hauch
 */
public class Main {
  /**
   * Compare two input stream
   * 
   * @param input1 the first stream
   * @param input2 the second stream
   * @return true if the streams contain the same content, or false otherwise
   * @throws IOException
   * @throws IllegalArgumentException if the stream is null
   */
  public static boolean isSame( InputStream input1,
                                InputStream input2 ) throws IOException {
      boolean error = false;
      try {
          byte[] buffer1 = new byte[1024];
          byte[] buffer2 = new byte[1024];
          try {
              int numRead1 = 0;
              int numRead2 = 0;
              while (true) {
                  numRead1 = input1.read(buffer1);
                  numRead2 = input2.read(buffer2);
                  if (numRead1 > -1) {
                      if (numRead2 != numRead1) return false;
                      // Otherwise same number of bytes read
                      if (!Arrays.equals(buffer1, buffer2)) return false;
                      // Otherwise same bytes read, so continue ...
                  } else {
                      // Nothing more in stream 1 ...
                      return numRead2 < 0;
                  }
              }
          } finally {
              input1.close();
          }
      } catch (IOException e) {
          error = true; // this error should be thrown, even if there is an error closing stream 2
          throw e;
      } catch (RuntimeException e) {
          error = true; // this error should be thrown, even if there is an error closing stream 2
          throw e;
      } finally {
          try {
              input2.close();
          } catch (IOException e) {
              if (!error) throw e;
          }
      }
  }
}

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