Boolean.java

/**
 *  Copyright 2007-2008 University Of Southern California
 *
 *  Licensed 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 edu.isi.pegasus.common.util;

/**
 * This class converts a boolean property specification (string) in various
 * representations into a booelan value. It is liberal in the representation
 * it accepts, but strict in what it produces.<p>
 *
 * @author Gaurang Mehta
 * @author Karan Vahi
 * @author Jens-S. Vöckler
 * @version $Revision$
 */
public class Boolean
{
  /**
   * The character representation of a <code>true</code> value.
   */
  public static final String TRUE = "true";

  /**
   * The character representation of a <code>false</code> value.
   */
  public static final String FALSE = "false";

  /**
   * Converts a boolean value into a strict representation of it.
   *
   * @param val is the boolean input value
   * @return a string representing the boolean value.
   */
  public static String print( boolean val )
  {
    return ( val ? TRUE : FALSE );
  }

  /**
   * Converts a boolean string representation into a boolean value.
   * Representations may include non-negative integers, where only
   * 0 means <code>false</code>. Other valid string representations
   * of  <code>true</code> include:
   *
   * <pre>
   * true
   * yes
   * on
   * </pre>
   *
   * Any other string representation is taken to mean <code>false</code>
   *
   * @param rep is the input string representing a boolean value.
   * @return a boolean value from the representation.
   */
  public static boolean parse( String rep )
  {
    return parse(rep,false);
  }

  /**
   * Converts a boolean string representation into a boolean value.
   * Representations may include non-negative integers, where only
   * 0 means <code>false</code>. Other valid string representations
   * of <code>true</code> include:
   *
   * <pre>
   * true
   * yes
   * on
   * </pre>
   *
   * Other valid string representations of <code>false</code> include,
   * besides the numerical zero:
   *
   * <pre>
   * false
   * no
   * off
   * </pre>
   *
   * Any other string representation is taken to mean the boolean value
   * indicated by the paramater deflt.
   *
   * @param rep is the input string representing a boolean value.
   * @param deflt is the deflt value to use in case rep does not
   * represent a valid boolean value.
   *
   * @return a boolean value from the representation.
   */
  public static boolean parse( String rep, boolean deflt )
  {
    if ( rep == null ) return deflt;
    String s = rep.trim().toLowerCase();
    if ( s.length() == 0 ) return deflt;

    if ( Character.isDigit(s.charAt(0)) ) {
      // check for number
      long value;
      try {
        value = Long.parseLong(s);
      } catch ( NumberFormatException nfe ) {
        value = deflt ? 1 : 0;
      }
      return ( value != 0 );
    } else {
      // check for key words
      return ( (s.equals("true") || s.equals("yes") || s.equals("on") ) ?
               true :
               ( (s.equals("false") || s.equals("no") || s.equals("off") )?
                 false :
                 deflt)
               );
    }
  }
}