如何从Java中的枚举中删除数组列表

Question

I need a way to remove array item declared as Filetype inside Enum in java class:

public enum Procedure {
    NONE("NONE", "procedure.none", false, null, Collections.<FileType> emptyList(), Collections.<FileType> emptyList()), 
    PROCEDUREF("PROCEDUREF", "procedure.procedureD", false, null, Arrays.asList(FileType.REQUEST), Arrays.asList(FileType.TEST1, FileType.TEST2,FileType.TEST3,FileType.TEST4,FileType.TEST5, FileType.TEST6,FileType.TEST7, FileType.TEST8, FileType.TEST9,FileType.TEST10, FileType.TEST11))
}

So I need to remove FileType.TEST10 from PROCEDUREF . I created a class to implement this enumeration:

public class FormObject {
    private static final List<Procedure> GUI_PROCEDURES = Arrays.asList(Procedure.NONE, Procedure.PROCEDUREF);

    public List<Procedure> getProcedures() {
        if (userdetail.ispilot()) {        
            GUI_PROCEDURES.get(1).getOptionalFileTypes().remove(10);
            return GUI_PROCEDURES;
        } 
    }

This instruction GUI_PROCEDURES.get(1).getOptionalFileTypes().remove(10); to remove FileType.TEST11 didn't work, could you please help me with this ? Thanks

Answer 1

It is hard to tell if you don't provide the error you are getting nor a minimal, complete and verifiable example.

Anyway, the error could be because you are trying to remove an element of an immutable List .

When you create a List with Arrays.asList what you get is an immutable list and if you try to call the method remove(10) a java.lang.UnsupportedOperationException exception will be thrown.

So probably you need to do some changes in your Procedure constructor to make those lists mutable. One way to do it is to create a new List from the immutable one. It would look similar to this:

Procedure(List<FileType> optionalFileTypes /* other arguments */) {
    this.optionalFileTypes = new ArrayList(optionalFileTypes);
    // other constructor code
}

Answer 2

Arrays.asList() doesn't support operations like add(),addAll(),remove(),removeAll() since it returns immutable list. You need to wrap any list which requires modification with ArrayList<>() . Try out something like below :

public enum Procedure {
    NONE("NONE", "procedure.none", false, null, Collections.<FileType> emptyList(), Collections.<FileType> emptyList()), 
   PROCEDUREF("PROCEDUREF", "procedure.procedureD", false, null, Arrays.asList(FileType.REQUEST), new ArrayList<>(Arrays.asList(FileType.TEST1, FileType.TEST2,FileType.TEST3,FileType.TEST4,FileType.TEST5, FileType.TEST6,FileType.TEST7, FileType.TEST8, FileType.TEST9,FileType.TEST10, FileType.TEST11)))}