java sample code

public class Main {

    static class Report {
        String id;
        ReportData data;
    }

    static abstract class ReportData {
        String id;
    }

    static class ReportDataTypeA extends ReportData {
        String section1;
        String section2;
    }

    static class ReportDataTypeB extends ReportData {
        String header;
        String section1a;
        String section1b;
    }

    static ReportData createDataByYear(int year) {
        if (year == 2021) {
            ReportDataTypeA reportData = new ReportDataTypeA();
            reportData.id = "1";
            reportData.section1 = "test1";
            return reportData;
        } else if (year == 2022) {
            ReportDataTypeB reportData = new ReportDataTypeB();
            reportData.id = "2";
            reportData.header = "header";
            return reportData;
        }
        return null;
    }

    public static void main(String... args) {
        Report report = new Report();
        report.data = createDataByYear(2021);
        System.out.println(report.data.id);
        report.data = createDataByYear(2022);
        System.out.println(report.data.id);
    }


}