Commons Math example source code file (RealVectorFormat.java)

This example Commons Math source code file (RealVectorFormat.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Math tags/keywords

arrayrealvector, default_separator, default_suffix, fieldposition, numberformat, override, parseposition, parseposition, realvectorformat, realvectorformat, string, string, stringbuffer, stringbuffer, text, util

The Commons Math RealVectorFormat.java source code

/*
 * 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.linear;

import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import org.apache.commons.math.MathRuntimeException;
import org.apache.commons.math.util.CompositeFormat;

/**
 * Formats a vector in components list format "{v0; v1; ...; vk-1}".
 * <p>The prefix and suffix "{" and "}" and the separator "; " can be replaced by
 * any user-defined strings. The number format for components can be configured.</p>
 * <p>White space is ignored at parse time, even if it is in the prefix, suffix
 * or separator specifications. So even if the default separator does include a space
 * character that is used at format time, both input string "{1;1;1}" and
 * " { 1 ; 1 ; 1 } " will be parsed without error and the same vector will be
 * returned. In the second case, however, the parse position after parsing will be
 * just after the closing curly brace, i.e. just before the trailing space.</p>
 *
 * @version $Revision: 783702 $ $Date: 2009-06-11 04:54:02 -0400 (Thu, 11 Jun 2009) $
 * @since 2.0
 */
public class RealVectorFormat extends CompositeFormat {

    /** Serializable version identifier */
    private static final long serialVersionUID = -708767813036157690L;

    /** The default prefix: "{". */
    private static final String DEFAULT_PREFIX = "{";

    /** The default suffix: "}". */
    private static final String DEFAULT_SUFFIX = "}";

    /** The default separator: ", ". */
    private static final String DEFAULT_SEPARATOR = "; ";

    /** Prefix. */
    private final String prefix;

    /** Suffix. */
    private final String suffix;

    /** Separator. */
    private final String separator;

    /** Trimmed prefix. */
    private final String trimmedPrefix;

    /** Trimmed suffix. */
    private final String trimmedSuffix;

    /** Trimmed separator. */
    private final String trimmedSeparator;

    /** The format used for components. */
    private NumberFormat format;

    /**
     * Create an instance with default settings.
     * <p>The instance uses the default prefix, suffix and separator:
     * "{", "}", and "; " and the default number format for components.</p>
     */
    public RealVectorFormat() {
        this(DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_SEPARATOR, getDefaultNumberFormat());
    }

    /**
     * Create an instance with a custom number format for components.
     * @param format the custom format for components.
     */
    public RealVectorFormat(final NumberFormat format) {
        this(DEFAULT_PREFIX, DEFAULT_SUFFIX, DEFAULT_SEPARATOR, format);
    }

    /**
     * Create an instance with custom prefix, suffix and separator.
     * @param prefix prefix to use instead of the default "{"
     * @param suffix suffix to use instead of the default "}"
     * @param separator separator to use instead of the default "; "
     */
    public RealVectorFormat(final String prefix, final String suffix,
                            final String separator) {
        this(prefix, suffix, separator, getDefaultNumberFormat());
    }

    /**
     * Create an instance with custom prefix, suffix, separator and format
     * for components.
     * @param prefix prefix to use instead of the default "{"
     * @param suffix suffix to use instead of the default "}"
     * @param separator separator to use instead of the default "; "
     * @param format the custom format for components.
     */
    public RealVectorFormat(final String prefix, final String suffix,
                            final String separator, final NumberFormat format) {
        this.prefix      = prefix;
        this.suffix      = suffix;
        this.separator   = separator;
        trimmedPrefix    = prefix.trim();
        trimmedSuffix    = suffix.trim();
        trimmedSeparator = separator.trim();
        this.format      = format;
    }

    /**
     * Get the set of locales for which real vectors formats are available.
     * <p>This is the same set as the {@link NumberFormat} set.

     * @return available real vector format locales.
     */
    public static Locale[] getAvailableLocales() {
        return NumberFormat.getAvailableLocales();
    }

    /**
     * Get the format prefix.
     * @return format prefix.
     */
    public String getPrefix() {
        return prefix;
    }

    /**
     * Get the format suffix.
     * @return format suffix.
     */
    public String getSuffix() {
        return suffix;
    }

    /**
     * Get the format separator between components.
     * @return format separator.
     */
    public String getSeparator() {
        return separator;
    }

    /**
     * Get the components format.
     * @return components format.
     */
    public NumberFormat getFormat() {
        return format;
    }

    /**
     * Returns the default real vector format for the current locale.
     * @return the default real vector format.
     */
    public static RealVectorFormat getInstance() {
        return getInstance(Locale.getDefault());
    }

    /**
     * Returns the default real vector format for the given locale.
     * @param locale the specific locale used by the format.
     * @return the real vector format specific to the given locale.
     */
    public static RealVectorFormat getInstance(final Locale locale) {
        return new RealVectorFormat(getDefaultNumberFormat(locale));
    }

    /**
     * This static method calls {@link #format(Object)} on a default instance of
     * RealVectorFormat.
     *
     * @param v RealVector object to format
     * @return A formatted vector
     */
    public static String formatRealVector(RealVector v) {
        return getInstance().format(v);
    }

    /**
     * Formats a {@link RealVector} object to produce a string.
     * @param vector 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(RealVector vector, StringBuffer toAppendTo,
                               FieldPosition pos) {

        pos.setBeginIndex(0);
        pos.setEndIndex(0);

        // format prefix
        toAppendTo.append(prefix);

        // format components
        for (int i = 0; i < vector.getDimension(); ++i) {
            if (i > 0) {
                toAppendTo.append(separator);
            }
            formatDouble(vector.getEntry(i), format, toAppendTo, pos);
        }

        // format suffix
        toAppendTo.append(suffix);

        return toAppendTo;

    }

    /**
     * Formats a object to produce a string.
     * <p>obj must be a  {@link RealVector} object. Any other type of
     * object will result in an {@link IllegalArgumentException} being thrown.</p>
     * @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 is not a valid type.
     */
    @Override
    public StringBuffer format(Object obj, StringBuffer toAppendTo,
                               FieldPosition pos) {

        if (obj instanceof RealVector) {
            return format( (RealVector)obj, toAppendTo, pos);
        }

        throw MathRuntimeException.createIllegalArgumentException(
              "cannot format a {0} instance as a real vector",
              obj.getClass().getName());

    }

    /**
     * Parses a string to produce a {@link RealVector} object.
     * @param source the string to parse
     * @return the parsed {@link RealVector} object.
     * @exception ParseException if the beginning of the specified string
     *            cannot be parsed.
     */
    public ArrayRealVector parse(String source) throws ParseException {
        ParsePosition parsePosition = new ParsePosition(0);
        ArrayRealVector result = parse(source, parsePosition);
        if (parsePosition.getIndex() == 0) {
            throw MathRuntimeException.createParseException(
                    parsePosition.getErrorIndex(),
                    "unparseable real vector: \"{0}\"", source);
        }
        return result;
    }

    /**
     * Parses a string to produce a {@link RealVector} object.
     * @param source the string to parse
     * @param pos input/ouput parsing parameter.
     * @return the parsed {@link RealVector} object.
     */
    public ArrayRealVector parse(String source, ParsePosition pos) {
        int initialIndex = pos.getIndex();

        // parse prefix
        parseAndIgnoreWhitespace(source, pos);
        if (!parseFixedstring(source, trimmedPrefix, pos)) {
            return null;
        }

        // parse components
        List<Number> components = new ArrayList();
        for (boolean loop = true; loop;){

            if (!components.isEmpty()) {
                parseAndIgnoreWhitespace(source, pos);
                if (!parseFixedstring(source, trimmedSeparator, pos)) {
                    loop = false;
                }
            }

            if (loop) {
                parseAndIgnoreWhitespace(source, pos);
                Number component = parseNumber(source, format, pos);
                if (component != null) {
                    components.add(component);
                } else {
                    // invalid component
                    // set index back to initial, error index should already be set
                    pos.setIndex(initialIndex);
                    return null;
                }
            }

        }

        // parse suffix
        parseAndIgnoreWhitespace(source, pos);
        if (!parseFixedstring(source, trimmedSuffix, pos)) {
            return null;
        }

        // build vector
        double[] data = new double[components.size()];
        for (int i = 0; i < data.length; ++i) {
            data[i] = components.get(i).doubleValue();
        }
        return new ArrayRealVector(data, false);

    }

    /**
     * Parses a string to produce a object.
     * @param source the string to parse
     * @param pos input/ouput parsing parameter.
     * @return the parsed object.
     * @see java.text.Format#parseObject(java.lang.String, java.text.ParsePosition)
     */
    @Override
    public Object parseObject(String source, ParsePosition pos) {
        return parse(source, pos);
    }

}