How to call a custom java class from hmc.xml

[Former Member]

How can I call a custom java class from hmc.xml .I tried adding a testclass.java in Core extension and added the reference in customeditor tag in hmc.xml ,but I am not able to clean and build .It throws the error cannot resolve the import de.hybris.platform.hmc.attribute.StringLayoutChip and de.hybris.platform.hmc.webchips.Chip.

The reason I need to add a custom class is ,I want to mask a custom text field in HMC .Cannot use CreditCardNumberEditorChip as it throws String indexOutOf bound exception for empty Strings .I can have empty string in that field. Is there an alternative way to achieve masking ?

Version of Hybris being used -6.1