process variable

i build a process, and ihave intilize a workflow variables as this (var1: contain values which user selected from multi selected box , var2: its a hidden field for storing the first value from var1(have default value 'empty') 

so i write a java code and put it inside a tool but it does not work , not storing the first value from the var1 to var 2 

this is the code 

import org.joget.apps.form.model.FormData;
import org.joget.apps.form.service.FormService;
import org.joget.commons.util.LogUtil;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class MultiSelectHandler {

    public void handleMultiSelectField(FormData formData, FormService formService) {
        // Get the multi-select field value from form data
        String multiSelectFieldName = "approversList";
        String fieldValue = formData.getFieldValue(multiSelectFieldName);
        
        if (fieldValue != null && !fieldValue.isEmpty()) {
            // Split the field value by semicolons to get a list of selected values
            List<String> selectedValues = Arrays.asList(fieldValue.split(";"));
            
            if (!selectedValues.isEmpty()) {
                // Get the first selected value
                String firstSelectedValue = selectedValues.get(0);
                
                // Store or use the first selected value as needed
                // For example, set it as a new value in the form data
                formData.getFieldValues().put("firstSelectedApprover", firstSelectedValue);
                
                // Optionally, log or further process the firstSelectedValue
                LogUtil.info(MultiSelectHandler.class.getName(), "First Selected Approver: " + firstSelectedValue);
            } else {
                LogUtil.info(MultiSelectHandler.class.getName(), "No values found after splitting.");
            }
        } else {
            LogUtil.info(MultiSelectHandler.class.getName(), "No values found in approversList.");
        }
    }
}