numberformat.java

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/* NumberFormat.java -- Formats and parses numbers
   Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.text;

import java.util.Locale;
import java.util.ResourceBundle;
import java.util.MissingResourceException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;

/**
 * This is the abstract superclass of all classes which format and 
 * parse numeric values such as decimal numbers, integers, currency values,
 * and percentages.  These classes perform their parsing and formatting
 * in a locale specific manner, accounting for such items as differing
 * currency symbols and thousands separators.
 * <p>
 * To create an instance of a concrete subclass of <code>NumberFormat</code>,
 * do not call a class constructor directly.  Instead, use one of the
 * static factory methods in this class such as 
 * <code>getCurrencyInstance</code>.
 * 
 * @author Tom Tromey <[e-mail]>
 * @author Aaron M. Renn ([e-mail])
 * @date March 4, 1999
 */
/* Written using "Java Class Libraries", 2nd edition, plus online
 * API docs for JDK 1.2 from http://www.javasoft.com.
 * Status:  Believed complete and correct to 1.2, except getAvailableLocales.
 */
public abstract class NumberFormat extends Format implements Cloneable
{
  /**
   * This is a constant used to create a <code>FieldPosition</code> object
   * that will return the integer portion of a formatted number.
   */
  public static final int INTEGER_FIELD = 0;

  /**
   * This is a constant used to create a <code>FieldPosition</code> object
   * that will return the fractional portion of a formatted number.
   */
  public static final int FRACTION_FIELD = 1;

  /**
   * This method is a specialization of the format method that performs
   * a simple formatting of the specified <code>long</code> number.
   *
   * @param number The <code>long</code> to format.
   *
   * @return The formatted number
   */
  public final String format (long number)
  {
    StringBuffer sbuf = new StringBuffer(50);
    format (number, sbuf, null);
    return sbuf.toString();
  }

  public final StringBuffer format (Object obj, StringBuffer sbuf,
				    FieldPosition pos)
  {
    if (obj instanceof Number)
      return format(((Number) obj).doubleValue(), sbuf, pos);
    else
      throw new IllegalArgumentException 
	("Cannot format given Object as a Number");
  }

  /**
   * This method formats the specified <code>double</code> and appends it to
   * a <code>StringBuffer</code>.
   * 
   * @param number The <code>double</code> to format.
   * @param sb The <code>StringBuffer</code> to append the formatted number to.
   * @param pos The desired <code>FieldPosition</code>.
   *
   * @return The <code>StringBuffer</code> with the appended number.
   */
  public abstract StringBuffer format (double number,
				       StringBuffer sbuf, FieldPosition pos);

  /**
   * This method formats the specified <code>long</code> and appends it to
   * a <code>StringBuffer</code>.
   * 
   * @param number The <code>long</code> to format.
   * @param sb The <code>StringBuffer</code> to append the formatted number to.
   * @param pos The desired <code>FieldPosition</code>.
   *
   * @return The <code>StringBuffer</code> with the appended number.
   */
  public abstract StringBuffer format (long number,
				       StringBuffer sbuf, FieldPosition pos);

  /**
   * This method tests the specified object for equality against this object.
   * This will be <code>true</code> if the following conditions are met:
   * <p>
   * <ul>
   * <li>The specified object is not <code>null</code>.
   * <li>The specified object is an instance of <code>NumberFormat</code>.
   * </ul>
   * <p>
   * Since this method does not test much, it is highly advised that 
   * concrete subclasses override this method.
   *
   * @param obj The <code>Object</code> to test against equality with
   *            this object. 
   * 
   * @return <code>true</code> if the specified object is equal to
   * this object, <code>false</code> otherwise. 
   */
  public boolean equals (Object obj)
  {
    if (! (obj instanceof NumberFormat))
      return false;
    NumberFormat nf = (NumberFormat) obj;
    return (groupingUsed == nf.groupingUsed
	    && maximumFractionDigits == nf.maximumFractionDigits
	    && maximumIntegerDigits == nf.maximumIntegerDigits
	    && minimumFractionDigits == nf.minimumFractionDigits
	    && minimumIntegerDigits == nf.minimumIntegerDigits
	    && parseIntegerOnly == nf.parseIntegerOnly);
  }

  /**
   * This method returns a list of locales for which concrete instances
   * of <code>NumberFormat</code> subclasses may be created.
   *
   * @return The list of available locales.
   */
  public static Locale[] getAvailableLocales ()
  {
    Locale[] list = new Locale[1];
    list[0] = Locale.US;
    return list;
  }

  private static final NumberFormat computeInstance (Locale loc,
						     String resource,
						     String def)
  {
    ResourceBundle res;
    try
      {
	res = ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
				       loc);
      }
    catch (MissingResourceException x)
      {
	res = null;
      }
    String fmt;
    try
      {
	fmt = res == null ? def : res.getString(resource);
      }
    catch (MissingResourceException x)
      {
	fmt = def;
      }
    DecimalFormatSymbols dfs = new DecimalFormatSymbols (loc);
    return new DecimalFormat (fmt, dfs);
  }

  /**
   * This method returns an instance of <code>NumberFormat</code> suitable
   * for formatting and parsing currency values in the default locale.
   *
   * @return An instance of <code>NumberFormat</code> for handling currencies.
   */
  public static final NumberFormat getCurrencyInstance ()
  {
    return getCurrencyInstance (Locale.getDefault());
  }

  /**
   * This method returns an instance of <code>NumberFormat</code> suitable
   * for formatting and parsing currency values in the specified locale.
   *
   * @return An instance of <code>NumberFormat</code> for handling currencies.
   */
  public static NumberFormat getCurrencyInstance (Locale loc)
  {
    return computeInstance (loc, "currencyFormat", "$#,##0.00;($#,##0.00)");
  }

  /**
   * This method returns a default instance for the default locale. This
   * will be a concrete subclass of <code>NumberFormat</code>, but the 
   * actual class returned is dependent on the locale.
   *
   * @return An instance of the default <code>NumberFormat</code> class.
   */
  public static final NumberFormat getInstance ()
  {
    return getInstance (Locale.getDefault());
  }

  /**
   * This method returns a default instance for the specified locale. This
   * will be a concrete subclass of <code>NumberFormat</code>, but the 
   * actual class returned is dependent on the locale.
   *
   * @param locale The desired locale.
   *
   * @return An instance of the default <code>NumberFormat</code> class.
   */
  public static NumberFormat getInstance (Locale loc)
  {
    // For now always return a number instance.
    return getNumberInstance (loc);
  }

  /**
   * This method returns the maximum number of digits allowed in the fraction
   * portion of a number.
   *
   * @return The maximum number of digits allowed in the fraction
   * portion of a number. 
   */
  public int getMaximumFractionDigits ()
  {
    return maximumFractionDigits;
  }

  /**
   * This method returns the maximum number of digits allowed in the integer
   * portion of a number.
   *
   * @return The maximum number of digits allowed in the integer
   * portion of a number. 
   */
  public int getMaximumIntegerDigits ()
  {
    return maximumIntegerDigits;
  }

  /**
   * This method returns the minimum number of digits allowed in the fraction
   * portion of a number.
   *
   * @return The minimum number of digits allowed in the fraction
   * portion of a number. 
   */
  public int getMinimumFractionDigits ()
  {
    return minimumFractionDigits;
  }

  /**
   * This method returns the minimum number of digits allowed in the integer
   * portion of a number.
   *
   * @return The minimum number of digits allowed in the integer
   * portion of a number. 
   */
  public int getMinimumIntegerDigits ()
  {
    return minimumIntegerDigits;
  }

  /**
   * This method returns a default instance for the specified locale. This
   * will be a concrete subclass of <code>NumberFormat</code>, but the 
   * actual class returned is dependent on the locale.