public class NewClass {
    
    public abstract void test;
    
    public void Exec(){
        test();
    }
    
}

public class NewClass2 {
    
    public void Method(){
        NewClass my;
        my.test = Show;
        my.Exec();
    }
    
    public void Show(){
        // тут делаем то что надо
    }
}

public interface ILogger {

    public void ShowMessage(String aMessage);
    public void ErrorMessage(String aMessage);

}
public class SAPMappingCustom {

    protected ILogger logger;

    protected void ShowMessage(String aMsg) {
        if (logger != null) {
            logger.ShowMessage(aMsg);
        }
    }

    protected void ErrorMessage(String aMsg) {
        if (logger != null) {
            logger.ErrorMessage(aMsg);
        }
    }

    public void SetLogger(ILogger aLogger){
        logger = aLogger;
    }
}
//Класс внешнего приложения
public class MappingOrderCSVToJDBC extends AbstractTransformation implements ILogger{

    private SAPMapping sap = new SAPMapping();

    public void transform(TransformationInput ti, TransformationOutput to) throws StreamTransformationException {
        isRunSAP = true;
        sap.SetLogger(this);
        sap.блаблабла;
    }

    @Override
    public void ShowMessage(String aMessage) {
        if (isRunSAP) {
            this.getTrace().addInfo(aMessage);
        }
        else {
            System.out.println(aMessage);
        }
    }

    @Override
    public void ErrorMessage(String aMessage) {
        ShowMessage(aMessage);
        throw new RuntimeException(aMessage);
    }
}