Interface instance
Right-click on "Object Library" - "Add Interface Instance", as shown in the figure below: the 
following window will pop up:
Enter the parameter information of the interface:
Click the interface "Sum", select the tab "Sum Operation", and click the add icon , as follows:
The following window pops up, check the method "counter(double, double)", as shown below:
After clicking OK, the display is as follows: 
Add rule
Click the rule package "related to java class" - "Add rule", and name it "Interface instance", as shown below:
Select the rule "Interface Instance" and click the down arrow, as shown below:
Click "Please click to select" - "Variable assignment", as shown below: 
Click "Please select" - "Sum" - "Sum.counter({arg1},{arg2})", as shown below:
The rules are configured as follows:
