Java I/O How to - Read and return the entire contents of the supplied Reader

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Question

We would like to know how to read and return the entire contents of the supplied Reader.

Answer

  /*from  ww w  .j a  va2  s .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.Reader;
/**
 * @author Randall Hauch
 */
public class Main {
  /**
   * Read and return the entire contents of the supplied {@link Reader}. This method always closes the reader when finished
   * reading.
   * 
   * @param reader the reader of the contents; may be null
   * @return the contents, or an empty string if the supplied reader is null
   * @throws IOException if there is an error reading the content
   */
  public static String read( Reader reader ) throws IOException {
      if (reader == null) return "";
      StringBuilder sb = new StringBuilder();
      boolean error = false;
      try {
          int numRead = 0;
          char[] buffer = new char[1024];
          while ((numRead = reader.read(buffer)) > -1) {
              sb.append(buffer, 0, numRead);
          }
      } catch (IOException e) {
          error = true; // this error should be thrown, even if there is an error closing reader
          throw e;
      } catch (RuntimeException e) {
          error = true; // this error should be thrown, even if there is an error closing reader
          throw e;
      } finally {
          try {
              reader.close();
          } catch (IOException e) {
              if (!error) throw e;
          }
      }
      return sb.toString();
  }
}

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