complexformat.java

Apache的common math数学软件包

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.
 */

package org.apache.commons.math.complex;

import java.io.Serializable;
import java.text.FieldPosition;
import java.text.Format;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.Locale;

/**
 * Formats a Complex number in cartesian format "Re(c) + Im(c)i".  'i' can
 * be replaced with 'j', and the number format for both real and imaginary parts
 * can be configured.
 *
 * @author Apache Software Foundation
 * @version $Revision: 480440 $ $Date: 2006-11-29 00:14:12 -0700 (Wed, 29 Nov 2006) $
 */
public class ComplexFormat extends Format implements Serializable {
    
    /** Serializable version identifier */
    private static final long serialVersionUID = -6337346779577272306L;
    
    /** The default imaginary character. */
    private static final String DEFAULT_IMAGINARY_CHARACTER = "i";
    
    /** The notation used to signify the imaginary part of the complex number. */
    private String imaginaryCharacter;
    
    /** The format used for the imaginary part. */
    private NumberFormat imaginaryFormat;

    /** The format used for the real part. */
    private NumberFormat realFormat;
    
    /**
     * Create an instance with the default imaginary character, 'i', and the
     * default number format for both real and imaginary parts.
     */
    public ComplexFormat() {
        this(DEFAULT_IMAGINARY_CHARACTER, getDefaultNumberFormat());
    }

    /**
     * Create an instance with a custom number format for both real and
     * imaginary parts.
     * @param format the custom format for both real and imaginary parts.
     */
    public ComplexFormat(NumberFormat format) {
        this(DEFAULT_IMAGINARY_CHARACTER, format);
    }
    
    /**
     * Create an instance with a custom number format for the real part and a
     * custom number format for the imaginary part.
     * @param realFormat the custom format for the real part.
     * @param imaginaryFormat the custom format for the imaginary part.
     */
    public ComplexFormat(NumberFormat realFormat,
            NumberFormat imaginaryFormat) {
        this(DEFAULT_IMAGINARY_CHARACTER, realFormat, imaginaryFormat);
    }
    
    /**
     * Create an instance with a custom imaginary character, and the default
     * number format for both real and imaginary parts.
     * @param imaginaryCharacter The custom imaginary character.
     */
    public ComplexFormat(String imaginaryCharacter) {
        this(imaginaryCharacter, getDefaultNumberFormat());
    }
    
    /**
     * Create an instance with a custom imaginary character, and a custom number
     * format for both real and imaginary parts.
     * @param imaginaryCharacter The custom imaginary character.
     * @param format the custom format for both real and imaginary parts.
     */
    public ComplexFormat(String imaginaryCharacter, NumberFormat format) {
        this(imaginaryCharacter, format, (NumberFormat)format.clone());
    }
    
    /**
     * Create an instance with a custom imaginary character, a custom number
     * format for the real part, and a custom number format for the imaginary
     * part.
     * @param imaginaryCharacter The custom imaginary character.
     * @param realFormat the custom format for the real part.
     * @param imaginaryFormat the custom format for the imaginary part.
     */
    public ComplexFormat(String imaginaryCharacter, NumberFormat realFormat,
            NumberFormat imaginaryFormat) {
        super();
        setImaginaryCharacter(imaginaryCharacter);
        setImaginaryFormat(imaginaryFormat);
        setRealFormat(realFormat);
    }

    /**
     * This static method calls formatComplex() on a default instance of
     * ComplexFormat.
     *
     * @param c Complex object to format
     * @return A formatted number in the form "Re(c) + Im(c)i"
     */
    public static String formatComplex( Complex c ) {
        return getInstance().format( c );
    }
    
    /**
     * Formats a {@link Complex} object to produce a string.
     *
     * @param complex the object to format.
     * @param toAppendTo where the text is to be appended
     * @param pos On input: an alignment field, if desired. On output: the
     *            offsets of the alignment field
     * @return the value passed in as toAppendTo.
     */
    public StringBuffer format(Complex complex, StringBuffer toAppendTo,
            FieldPosition pos) {
        
        pos.setBeginIndex(0);
        pos.setEndIndex(0);

        // format real
        double re = complex.getReal();
        formatDouble(re, getRealFormat(), toAppendTo, pos);
        
        // format sign and imaginary
        double im = complex.getImaginary();
        if (im < 0.0) {
            toAppendTo.append(" - ");
            formatDouble(-im, getImaginaryFormat(), toAppendTo, pos);
            toAppendTo.append(getImaginaryCharacter());
        } else if (im > 0.0 || Double.isNaN(im)) {
            toAppendTo.append(" + ");
            formatDouble(im, getImaginaryFormat(), toAppendTo, pos);
            toAppendTo.append(getImaginaryCharacter());
        }
        
        return toAppendTo;
    }
    
    /**
     * Formats a object to produce a string.  <code>obj</code> must be either a 
     * {@link Complex} object or a {@link Number} object.  Any other type of
     * object will result in an {@link IllegalArgumentException} being thrown.
     *
     * @param obj the object to format.
     * @param toAppendTo where the text is to be appended
     * @param pos On input: an alignment field, if desired. On output: the
     *            offsets of the alignment field
     * @return the value passed in as toAppendTo.
     * @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer, java.text.FieldPosition)
     * @throws IllegalArgumentException is <code>obj</code> is not a valid type.
     */
    public StringBuffer format(Object obj, StringBuffer toAppendTo,
            FieldPosition pos) {
        
        StringBuffer ret = null;
        
        if (obj instanceof Complex) {
            ret = format( (Complex)obj, toAppendTo, pos);
        } else if (obj instanceof Number) {
            ret = format( new Complex(((Number)obj).doubleValue(), 0.0),
                toAppendTo, pos);
        } else { 
            throw new IllegalArgumentException(
                "Cannot format given Object as a Date");
        }
        
        return ret;
    }

    /**
     * Formats a double value to produce a string.  In general, the value is
     * formatted using the formatting rules of <code>format</code>.  There are
     * three exceptions to this:
     * <ol>
     * <li>NaN is formatted as '(NaN)'</li>
     * <li>Positive infinity is formatted as '(Infinity)'</li>
     * <li>Negative infinity is formatted as '(-Infinity)'</li>
     * </ol>
     *
     * @param value the double to format.
     * @param format the format used.
     * @param toAppendTo where the text is to be appended
     * @param pos On input: an alignment field, if desired. On output: the
     *            offsets of the alignment field
     * @return the value passed in as toAppendTo.
     */
    private StringBuffer formatDouble(double value, NumberFormat format,
            StringBuffer toAppendTo, FieldPosition pos) {
        if( Double.isNaN(value) || Double.isInfinite(value) ) {
            toAppendTo.append('(');
            toAppendTo.append(value);
            toAppendTo.append(')');
        } else {
            format.format(value, toAppendTo, pos);
        }
        return toAppendTo;
    }
    
    /**
     * Get the set of locales for which complex formats are available.  This
     * is the same set as the {@link NumberFormat} set. 
     * @return available complex format locales.
     */
    public static Locale[] getAvailableLocales() {
        return NumberFormat.getAvailableLocales();
    }
    
    /**
     * Create a default number format.  The default number format is based on
     * {@link NumberFormat#getInstance()} with the only customizing is the
     * maximum number of fraction digits, which is set to 2.  
     * @return the default number format.
     */
    private static NumberFormat getDefaultNumberFormat() {
        return getDefaultNumberFormat(Locale.getDefault());
    }
    
    /**
     * Create a default number format.  The default number format is based on
     * {@link NumberFormat#getInstance(java.util.Locale)} with the only
     * customizing is the maximum number of fraction digits, which is set to 2.  
     * @param locale the specific locale used by the format.
     * @return the default number format specific to the given locale.
     */
    private static NumberFormat getDefaultNumberFormat(Locale locale) {
        NumberFormat nf = NumberFormat.getInstance(locale);
        nf.setMaximumFractionDigits(2);
        return nf;
    }
    
    /**
     * Access the imaginaryCharacter.
     * @return the imaginaryCharacter.
     */
    public String getImaginaryCharacter() {
        return imaginaryCharacter;
    }
    
    /**
     * Access the imaginaryFormat.
     * @return the imaginaryFormat.
     */
    public NumberFormat getImaginaryFormat() {
        return imaginaryFormat;
    }
    
    /**
     * Returns the default complex format for the current locale.
     * @return the default complex format.