Call "java -jar MyFile.jar" with additional classpath option

I created a jar file containing all my compiled stuff. Additionally my ant build script copies the required libs into a subfolder "libs". The structure looks like this:

MyProgram.jarlibs/

So when I try to run my program now I get the following error:

java -cp ".:/home/user/java/MyProgram/jar/libs" -jar MyProgram.jarjava.lang.ClassNotFoundException: org.postgresql.Driver    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)    at java.security.AccessController.doPrivileged(Native Method)    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)    at java.lang.Class.forName0(Native Method)    at java.lang.Class.forName(Class.java:186)    at database.PostgresQL.getConnection(PostgresQL.java:38)    at recommender.dao.Creative2IdxDAO.createCreatives2Idx(Creative2IdxDAO.java:19)    at main.Main.calculateCorrelationMatrix(Main.java:51)    at main.Main.main(Main.java:28)java.lang.NullPointerException    at recommender.dao.Creative2IdxDAO.createCreatives2Idx(Creative2IdxDAO.java:25)    at main.Main.calculateCorrelationMatrix(Main.java:51)    at main.Main.main(Main.java:28)

Why does this happen?