How to build an hierarchy tree of categories in java using enums or any other way?

Question

Assuming that we have a set of categories: categories={A,B}. Let\'s assume more that A consists of subcategories: {A1,A2,A3} and B consists of subcategories: {B1,B2}.In addi

Answer 1

In addition to the answers above, I would like to share something I found on the internet too. I have not tested it yet, but it seems to offer an alternative:

http://alexradzin.blogspot.hk/2010/10/hierarchical-structures-with-java-enums_05.html

public enum OsType {
OS(null),
    Windows(OS),
        WindowsNT(Windows),
            WindowsNTWorkstation(WindowsNT),
            WindowsNTServer(WindowsNT),
        Windows2000(Windows),
            Windows2000Server(Windows2000),
            Windows2000Workstation(Windows2000),
        WindowsXp(Windows),
        WindowsVista(Windows),
        Windows7(Windows),
        Windows95(Windows),
        Windows98(Windows),
    Unix(OS) {
            @Override
            public boolean supportsXWindows() {
                return true;
            }
        },
        Linux(Unix),
        AIX(Unix),
        HpUx(Unix),
        SunOs(Unix),
;
private OsType parent = null;

private OsType(OsType parent) {
    this.parent = parent;
}