main/classes/core/src/com/ibm/icu/util/ListFormatter.java

/*
 *******************************************************************************
 * Copyright (C) 2012-2012, Google, International Business Machines Corporation and
 * others. All Rights Reserved.
 *******************************************************************************
 */
package com.ibm.icu.util;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;

/**
 * Immutable class for formatting a list, using data from CLDR (or supplied
 * separately). The class is not subclassable.
 * 
 * @author markdavis
 * @draft ICU 50
 * @provisional This API might change or be removed in a future release.
 */
final public class ListFormatter {
    private final String two;
    private final String start;
    private final String middle;
    private final String end;

    /**
     * <b>Internal:</b> Create a ListFormatter from component strings,
     * with definitions as in LDML.
     * 
     * @param two
     *            string for two items, containing {0} for the first, and {1}
     *            for the second.
     * @param start
     *            string for the start of a list items, containing {0} for the
     *            first, and {1} for the rest.
     * @param middle
     *            string for the start of a list items, containing {0} for the
     *            first part of the list, and {1} for the rest of the list.
     * @param end
     *            string for the end of a list items, containing {0} for the
     *            first part of the list, and {1} for the last item.
     * @internal
     */
    public ListFormatter(String two, String start, String middle, String end) {
        this.two = two;
        this.start = start;
        this.middle = middle;
        this.end = end;
    }

    /**
     * Create a list formatter that is appropriate for a locale.
     * 
     * @param locale
     *            the locale in question.
     * @return ListFormatter
     * @draft ICU 50
     * @provisional This API might change or be removed in a future release.
     */
    public static ListFormatter getInstance(ULocale locale) {
        // These can be cached, since they are read-only
        // poor-man's locale lookup, for hardcoded data
        while (true) {
            ListFormatter data = localeToData.get(locale);
            if (data != null) {
                return data;
            }
            locale = locale.equals(zhTW) ? ULocale.TRADITIONAL_CHINESE : locale.getFallback();
            if (locale == null) return localeToData.get(ULocale.ROOT);
        }
    }
    private static ULocale zhTW = new ULocale("zh_TW");

    /**
     * Create a list formatter that is appropriate for a locale.
     * 
     * @param locale
     *            the locale in question.
     * @return ListFormatter
     * @draft ICU 50
     * @provisional This API might change or be removed in a future release.
     */
    public static ListFormatter getInstance(Locale locale) {
        return getInstance(ULocale.forLocale(locale));
    }

    /**
     * Format a list of objects.
     * 
     * @param items
     *            items to format. The toString() method is called on each.
     * @return items formatted into a string
     * @draft ICU 50
     * @provisional This API might change or be removed in a future release.
     */
    public String format(Object... items) {
        return format(Arrays.asList(items));
    }

    /**
     * Format a collection of objects. The toString() method is called on each.
     * 
     * @param items
     *            items to format. The toString() method is called on each.
     * @return items formatted into a string
     * @draft ICU 50
     * @provisional This API might change or be removed in a future release.
     */
    public String format(Collection<Object> items) {
        // TODO optimize this for the common case that the patterns are all of the
        // form {0}<sometext>{1}.
        // We avoid MessageFormat, because there is no "sub" formatting.
        Iterator<Object> it = items.iterator();
        int count = items.size();
        switch (count) {
        case 0:
            return "";
        case 1:
            return it.next().toString();
        case 2:
            return format2(two, it.next(), it.next());
        }
        String result = it.next().toString();
        result = format2(start, result, it.next());
        for (count -= 3; count > 0; --count) {
            result = format2(middle, result, it.next());
        }
        return format2(end, result, it.next());
    }

    private String format2(String pattern, Object a, Object b) {
        int i0 = pattern.indexOf("{0}");
        int i1 = pattern.indexOf("{1}");
        if (i0 < 0 || i1 < 0) {
            throw new IllegalArgumentException("Missing {0} or {1} in pattern " + pattern);
        }
        return i0 < i1
            ? pattern.substring(0, i0) + a + pattern.substring(i0+3, i1) + b + pattern.substring(i1+3)
            : pattern.substring(0, i1) + a + pattern.substring(i1+3, i0) + b + pattern.substring(i0+3);
    }

    /** JUST FOR DEVELOPMENT */
    // For use with the hard-coded data
    // TODO Replace by use of RB
    // Verify in building that all of the patterns contain {0}, {1}.

    static Map<ULocale, ListFormatter> localeToData = new HashMap<ULocale, ListFormatter>();
    static void add(String locale, String...data) {
        localeToData.put(new ULocale(locale), new ListFormatter(data[0], data[1], data[2], data[3]));
    }
    static {
        ListFormatterData.load();
    }
}