why get error when import librec in net beans

Please use maven to manage the packages, here is the pom.xml.
<!--

Copyright (C) 2016 LibRec
LibRec is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

LibRec is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with LibRec. If not, see <http://www.gnu.org/licenses/>.
-->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.librec</groupId>
    <packaging>jar</packaging>
    <artifactId>librec-core</artifactId>
    <version>2.0.0</version>
    <name>librec-core</name>
    <url>http://www.librec.net</url>
    <description>LibRec is A Java Library for Recommender Systems</description>
    <licenses>
        <license>
            <name>GNU GENERAL PUBLIC LICENSE Version 3, 29 June 2007</name>
            <url>
                https://github.com/guoguibing/librec/blob/2.0.0/LICENSE
            </url>
        </license>
    </licenses>
    <developers>
        <developer>
            <name>wangyufeng</name>
            <email>wangyufengkevin@gmail.com</email>
        </developer>
    </developers>
    <scm>
        <connection>scm:git:git@github.com:guoguibing/librec.git</connection>
        <developerConnection>scm:git:git@github.com:guoguibing/librec.git</developerConnection>
        <url>scm:git:git@github.com:guoguibing/librec.git</url>
    </scm>
    <dependencies>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>commons-cli</groupId>
            <artifactId>commons-cli</artifactId>
            <version>1.3</version>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>15.0</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
                <dependency>
                       <groupId>net.librec</groupId>
                       <artifactId>librec-core</artifactId>
                       <version>2.0.0</version>
                 </dependency>
    </dependencies>
</project>
guoguibing / librec

why get error when import librec in net beans #184
