我是hadoop新手，尝试直接使用hadoop文件系统在标准输出上显示hadoop文件系统中的文件内容，但出现以下错误。

import java.io.InputStream;
import java.net.URI;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;

public class FileSystemCat {

		public static void main(String[] args) throws Exception {
			Configuration conf = new Configuration();
		    conf.addResource(new Path("/usr/local/hadoop/etc/hadoop/core-site.xml"));
		    conf.addResource(new Path("/usr/local/hadoop/etc/hadoop/hdfs-site.xml"));
		  String uri = "/books/pg5000.txt";
		FileSystem fs = FileSystem.get(URI.create(uri), conf);
		InputStream in = null;
		try {
			in = fs.open(new Path(uri));
			IOUtils.copyBytes(in, System.out, 4096, false);
			} finally {
			IOUtils.closeStream(in);
			}
		}
}

错误-

Exception in thread "main" java.lang.NoClassDefFoundError: org/slf4j/LoggerFactory
    at org.apache.hadoop.security.authentication.util.KerberosName.<clinit>(KerberosName.java:43)
    at org.apache.hadoop.security.UserGroupInformation.initialize(UserGroupInformation.java:261)
    at org.apache.hadoop.security.UserGroupInformation.ensureInitialized(UserGroupInformation.java:248)
    at org.apache.hadoop.security.UserGroupInformation.loginUserFromSubject(UserGroupInformation.java:763)
    at org.apache.hadoop.security.UserGroupInformation.getLoginUser(UserGroupInformation.java:748)
    at 

    org.apache.hadoop.security.UserGroupInformation.getCurrentUser(UserGroupInformation.java:621)
        at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2753)
        at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2745)
        at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2611)
        at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:370)
        at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:169)
        at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:354)
        at FileSystemCat.main(FileSystemCat.java:17)
    Caused by: java.lang.ClassNotFoundException: org.slf4j.LoggerFactory
        at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
        ... 13 more

有人能指引我，我错在哪里？