001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2015 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.Properties;
023
024/**
025 * Resolves external properties from an
026 * underlying {@code Properties} object.
027 *
028 * @author lkuehne
029 */
030public final class PropertiesExpander
031    implements PropertyResolver {
032    /** The underlying Properties object. */
033    private final Properties properties = new Properties();
034
035    /**
036     * Creates a new PropertiesExpander.
037     * @param properties the underlying properties to use for
038     *     property resolution.
039     * @throws IllegalArgumentException indicates null was passed
040     * @noinspection CollectionDeclaredAsConcreteClass
041     */
042    public PropertiesExpander(Properties properties) {
043        if (properties == null) {
044            throw new IllegalArgumentException("cannot pass null");
045        }
046        this.properties.putAll(properties);
047    }
048
049    @Override
050    public String resolve(String name) {
051        return properties.getProperty(name);
052    }
053}