title: how to fix java.lang.NoClassDefFoundError: org/apache/commons/net/ntp/NTPUDPClient
body: <p>I downloaded commons-net-3.1.jar on this website:</p>
  <p><a href="https://jar-download.com/maven-repository-class-search.php?search_box=org.apache.commons.net.ntp.NTPUDPClient" rel="nofollow noreferrer">https://jar-download.com/maven-repository-class-search.php?search_box=org.apache.commons.net.ntp.NTPUDPClient</a></p>
  <p>it worked fine, but now I get this error:</p>
  <blockquote>
  <p>Exception in thread &quot;main&quot; java.lang.NoClassDefFoundError: org/apache/commons/net/ntp/NTPUDPClient</p>
  </blockquote>
  <blockquote>
  <p>Caused by: java.lang.ClassNotFoundException: org.apache.commons.net.ntp.NTPUDPClient
  at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:602)
  at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
  at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
  ... 1 more</p>
  </blockquote>
  <p>Can someone help me to fix this problem? I already searched for a solution, but I just find android threads without a solution for my problem.</p>
  <p>Edit: I am using javaSE-14 (java-JDK) and eclipse. I am using the standard javaSE-14 library and a new created library with commons-net-3.7.jar (from Uroš answer), but I still have the same error. (I am not using a maven projekt, I am using a normal java projekt)
  I tried to install the jar into my pom.xml with this text:</p>
  <pre><code>     &lt;dependency&gt;
          &lt;groupId&gt;commons-net&lt;/groupId&gt;
          &lt;artifactId&gt;commons-net&lt;/artifactId&gt;
          &lt;version&gt;3.7&lt;/version&gt;
      &lt;scope&gt;system&lt;/scope&gt;
      &lt;systemPath&gt;
      C:\Users\denni\Downloads\Apache jar\commons-net-3.7.jar
      &lt;/systemPath&gt;
      &lt;/dependency&gt;
  </code></pre>
  <p>I also tried the text that was written below, but I still have the same problem</p>
  <pre><code>       &lt;dependency&gt;
          &lt;groupId&gt;commons-net&lt;/groupId&gt;
          &lt;artifactId&gt;commons-net&lt;/artifactId&gt;
          &lt;version&gt;3.7&lt;/version&gt;
      &lt;/dependency&gt;
  
  
  
  
  
  
  import java.net.InetAddress;
  import java.util.Date;
  
  import org.apache.commons.net.ntp.NTPUDPClient;
  import org.apache.commons.net.ntp.TimeInfo;
  
  
  
  public class time {
      public static void main(String[] args) throws Exception {    
               NTPUDPClient client = new NTPUDPClient();
               client.open();
               // use host name or IP address of target NTP server
               InetAddress hostAddr = InetAddress.getByName(&quot;pool.ntp.org&quot;);
               TimeInfo info = client.getTime(hostAddr);
               info.computeDetails(); // compute offset/delay if not already done
               Long offsetValue = info.getOffset();
               Long delayValue = info.getDelay();
               String delay = (delayValue == null) ? &quot;N/A&quot; : delayValue.toString();
               String offset = (offsetValue == null) ? &quot;N/A&quot; : offsetValue.toString();
      
               System.out.println(&quot; Roundtrip delay(ms)=&quot; + delay
                               + &quot;, clock offset(ms)=&quot; + offset); // offset in ms
               client.close();
      }
  }
  </code></pre>