001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2018 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle;
021
022import java.util.Enumeration;
023import java.util.HashMap;
024import java.util.Map;
025import java.util.Properties;
026
027/**
028 * Resolves external properties from an
029 * underlying {@code Properties} object.
030 *
031 */
032public final class PropertiesExpander
033    implements PropertyResolver {
034
035    /** The underlying values. */
036    private final Map<String, String> values;
037
038    /**
039     * Creates a new PropertiesExpander.
040     * @param properties the underlying properties to use for
041     *     property resolution.
042     * @throws IllegalArgumentException indicates null was passed
043     */
044    public PropertiesExpander(Properties properties) {
045        if (properties == null) {
046            throw new IllegalArgumentException("cannot pass null");
047        }
048        values = new HashMap<>(properties.size());
049        for (Enumeration<?> e = properties.propertyNames(); e.hasMoreElements();) {
050            final String name = (String) e.nextElement();
051            values.put(name, properties.getProperty(name));
052        }
053    }
054
055    @Override
056    public String resolve(String name) {
057        return values.get(name);
058    }
059
060}