public MultiPartSpecBuilder controlName(String controlName) {
        Validate.notEmpty(controlName, "Control name cannot be empty");
        this.controlName = controlName;
        this.isControlNameExplicit = true;
        return this;
    }
public MultiPartSpecBuilder controlName(String controlName) {
        Validate.notEmpty(controlName, "Control name cannot be empty");
        this.controlName = controlName;
        this.isControlNameExplicit = true;
        return this;
    }
public MultiPartSpecBuilder controlName ( String controlName ) { Validate . notEmpty ( controlName , "Control name cannot be empty" ) ; this . controlName = controlName ; this . isControlNameExplicit = true ; return this ; }
Specify the control name of this multi-part.

@param controlName The control name to use. Default is <code>file</code>.
@return An instance of MultiPartSpecBuilder
Specify the control name of this multi - part .