See full tutorial here : https://cedricleruth.com/how-to-set-current-column-value-of-selected-richtable-row-from-iterator-in-oracle-adf/

setRichTableSelectedRowAttributeValue.java

//Function to call as follow : 
//setRichTableSelectedRowAttributeValue("YOUR_TABLE_JSF_ID", "YOUR_VO_ATTRIBUTE_NAME", "THE_NEW_VALUE_TO_SET");

public void setRichTableSelectedRowAttributeValue(String tableID, String attributeName, Object newAttributeValueToSet) {
    Object value = null;
    RichTable richTable = (RichTable)JSFUtils.findComponentInRoot(tableID);
    if (richTable != null) {
        RowKeySet rks = richTable.getSelectedRowKeys();
        Iterator it = rks.iterator();
        while (it.hasNext()) {
            List selectedRowKeyPath = (List)it.next();
            Row row = ((JUCtrlHierNodeBinding)richTable.getRowData(selectedRowKeyPath)).getRow();
            row.setAttribute(attributeName, newAttributeValueToSet); //Be sure that the attributeName is defined in the VO to avoid errors
          //Note : The attributeName is the name of the table column as written in the View Object (It is case sensitive)
        }
    }
}


//The function use the findComponentInRoot util, usually set in a bean called JSFUtils. If you don't have it already here it is:
 /**
 * Method find in the JSFUtils ADF toolkit: https://github.com/CedricL46/Oracle-ADF-and-JSF-Utils-libraries
 * Locate an UIComponent in view root with its component id. Use a recursive way to achieve this.
 * @param id UIComponent id
 * @return UIComponent object
 */
public static UIComponent findComponentInRoot(String id) {
    UIComponent component = null;
    if (id != null) {
        FacesContext facesContext = FacesContext.getCurrentInstance();
        if (facesContext != null) {
            UIComponent root = facesContext.getViewRoot();
            if (root != null) {
                component = findComponent(root, id);
            }
        }
    }
    return component;
}