Project project = CreateTestProjectWithCustomField();
Task task = project.getRootTask().getChildren().getById(1);

// EvaluateStrConv
// Set formulas and print extended attribute value
project.getExtendedAttributes().get(0).setFormula("StrConv(\"sTring and sTRINg\",3)");
System.out.println(task.getExtendedAttributes().get(0).getTextValue());
        
project.getExtendedAttributes().get(0).setFormula("StrConv(\"sTring and sTRINg\",1)");
System.out.println(task.getExtendedAttributes().get(0).getTextValue());
        
project.getExtendedAttributes().get(0).setFormula("StrConv(\"sTring and sTRINg\",2)");
System.out.println(task.getExtendedAttributes().get(0).getTextValue());
   
// EvaluateStringFunction
// Set formulas and print extended attribute value
project.getExtendedAttributes().get(0).setFormula("String(5, 40)");
System.out.println(task.getExtendedAttributes().get(0).getTextValue());
        
project.getExtendedAttributes().get(0).setFormula("String(5, \"A\")");
System.out.println(task.getExtendedAttributes().get(0).getTextValue());
        
project.getExtendedAttributes().get(0).setFormula("String(-5, \"A\")");
// #Error
System.out.println(task.getExtendedAttributes().get(0).getTextValue());