Find serialver for class with reference to java.sql.Timestamp

I have a simple class with reference to java.sql.Timestamp. Any class with a reference to this class doesn't give serialver unique id. For example, I am not able to find serial version id for java.sql.Timestamp or the class which refers to this.

serialver -classpath . java.sql.Timestamp 

error: Class java.sql.Timestamp not found.

If I have reference to java.sql.Timestamp in MyCustomPOJO in jar custom.jar

serialver -classpath custom.jar com.org.domain.MyCustomPOJO 
Exception in thread "main" java.lang.NoClassDefFoundError: com/org/domain/MyCustomPOJO
    at java.base/java.lang.Class.getDeclaredFields0(Native Method)
    at java.base/java.lang.Class.privateGetDeclaredFields(Class.java:3297)
    at java.base/java.lang.Class.getDeclaredField(Class.java:2608)
    at java.base/java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:246)
    at jdk.compiler/sun.tools.serialver.SerialVer.main(SerialVer.java:188)
    Caused by: java.lang.ClassNotFoundException: java.sql.Timestamp
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:592)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:525)
    ... 31 more

Any one know how to find serialversion id for java.sql.Timestamp Or custom class which has reference to Timestamp?

Since Java 9, Java classes have been organized into modules. See Java Platform Module System at Wikipedia.

By default, the only module visible to a Java runtime is java.base. serialver does not see other modules, such as the java.sql module that contains the Timestamp class.

You can tell serialver to include other modules by using -J to pass a java command-line option:

serialver -J--add-modules=java.sql -classpath custom.jar com.org.domain.MyCustomPOJO