<p>I solved this problem but UBCG.JAR does not work with java 11 . It is necessary to install openjdk-8-jre and switch the default java.</p>
<p><strong>Install openjdk-8-jre</strong></p>
<pre><code><span class="math-container">$ sudo apt-cache policy openjdk-8-jre
$</span> sudo apt install openjdk-8-jre=1.8.0_292
</code></pre>
<p><strong>Switch the default java</strong></p>
<pre><code>$ sudo update-alternatives --config java
*            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081  
</code></pre>
<p><strong>Checking the default java</strong></p>
<pre><code>    $ java -version
</code></pre>
<p>openjdk version &quot;1.8.0_292&quot;
OpenJDK Runtime Environment (build 1.8.0_292-8u292-b10-0ubuntu1~18.04-b10)
OpenJDK 64-Bit Server VM (build 25.292-b10, mixed mode)</p>
<p><strong>Run the UBGC.jar</strong></p>
<pre><code>$ java -jar UBCG.jar 
      ###############################
      #         UBCG ver. 3.0       #
      ###############################
</code></pre>

CC BY-SA 4.0
2021-06-23T17:56:19.397Z
2021-06-23T20:50:30.350Z
2021-06-23T20:50:30.350Z
Fabio
<p>You are probably using the wrong java version it should be 8</p>
<p>try &quot;java -version&quot;</p>

CC BY-SA 4.0
2020-07-19T14:00:58.263Z
2020-07-19T14:00:58.263Z
Chris
<p>I wanna install UBCG.JAR in ubuntu 18.04 but I cannot run the java File UBCG.JAR.
when I type the code <code>java -jar UBCG.JAR</code> an error message appears.</p>
<pre><code>Exception in thread &quot;main&quot; java.lang.NoClassDefFoundError: org/json/simple/parser/ParseException
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:56)
</code></pre>
<p>Caused by: java.lang.ClassNotFoundException: org.json.simple.parser.ParseException
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
... 3 more</p>
<pre><code>$ java -version
Openjdk version &quot;11.0.7&quot; 2020-04-14
</code></pre>

CC BY-SA 4.0
2021-11-06T00:11:38.443Z
Thank you very much the problem solved, it was about JDK version
Maloki
CC BY-SA 4.0
2022-03-21T21:28:31.163Z
Could you please either accept an answer, or write up (and accept) your own solution to this problem?
gringer
<java>
Java error when trying to run UBCG jar (java.lang.ClassNotFoundException)
# Java error when trying to run UBCG jar (java.lang.ClassNotFoundException)

(Asked by: username_0 on 2019-12-14)

I wanna install UBCG.JAR in ubuntu 18.04 but I cannot run the java File UBCG.JAR.
when I type the code java -jar UBCG.JAR an error message appears.
Exception in thread "main" java.lang.NoClassDefFoundError: org/json/simple/parser/ParseException
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:56)

Caused by: java.lang.ClassNotFoundException: org.json.simple.parser.ParseException
at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
... 3 more
$ java -version
Openjdk version "11.0.7" 2020-04-14

**Tags:** java
> **Comments:**
> **username_0**: Thank you very much the problem solved, it was about JDK version  
> **username_1**: Could you please either accept an answer, or write up (and accept) your own solution to this problem?  

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## 2 answers

### Answer by username_2 on 2021-06-23. Score: 0

I solved this problem but UBCG.JAR does not work with java 11 . It is necessary to install openjdk-8-jre and switch the default java.
Install openjdk-8-jre
$ sudo apt-cache policy openjdk-8-jre
$ sudo apt install openjdk-8-jre=1.8.0_292

Switch the default java
$ sudo update-alternatives --config java
*            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081  

Checking the default java
    $ java -version

openjdk version "1.8.0_292"
OpenJDK Runtime Environment (build 1.8.0_292-8u292-b10-0ubuntu1~18.04-b10)
OpenJDK 64-Bit Server VM (build 25.292-b10, mixed mode)
Run the UBGC.jar
$ java -jar UBCG.jar 
      ###############################
      #         UBCG ver. 3.0       #
      ###############################


---

### Answer by username_3 on 2020-07-19. Score: 0

You are probably using the wrong java version it should be 8

try "java -version"


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