I tried to create multiple JRConditionalStyle in Java code for the Jasper report.

private JRDesignStyle getThicknessMeasureStyle(String fieldName, String fieldName1, String fieldName2, JRDesignStyle parentStyle) {
    JRDesignStyle jrDesignStyle = new JRDesignStyle();
    jrDesignStyle.setName(fieldName + "Style");
    jrDesignStyle.setParentStyle(parentStyle);
    String prefix = "placethicknesstmlpoint.";
    List<String> values = getValues();
    for (int i=0; i<3; i++) {
        JRDesignConditionalStyle conditionalStyle = new JRDesignConditionalStyle();
        conditionalStyle.rename("Style" + i);
        JRDesignExpression conditionExpression = new JRDesignExpression();
        conditionExpression.setText(String.format("method1.cal($F{%s}, $F{%s, %F{%s}}).equals(${%s})", fieldName, fieldName1, fieldName2, values(i));
        conditionalStyle.setConditionExpression(conditionExpression);
        conditionalStyle.setBackcolor(#123456);
        conditionalStyle.setMode(OPAQUE);
        jrDesignStyle.addConditionalStyle(conditionalStyle);
    }
    return jrDesignStyle;
}

error

net.sf.jasperreports.engine.design.JRValidationException: Report design not valid : 
     1. Field name missing.

Stanger thing is I tried to write this JRDesignExpression in the jrxml file, it works