Enum static or non-static method

Question

Consider the following enum class

public enum ClassA {
    CHECK1("X", 0),
    CHECK2("Y", 2),
    CHECK3("Z", 1);

    private final String id;
    private final String cdValue;

    private ClsA(String id, String cdValue) {
        this.id = id;
        this.cdValue = cdValue;
    }

    private String getId() {
        return id;
    }

    private String getCdValue() {
        return cdValue ;
    }

    private static final List<String> cdValues = new ArrayList<String>();

    static {
        for (ClassA clsA : ClassA.values()) {   
            cdValues.add(clsA.getCdValue());    
        }
    }   

    public boolean isCdValue(String cdValue)
    {
        if clsValues.contains(cdValue)
            return true;
        else return false;
    }   
}

The question that I have is does the method isCdValue has to be static. I have to use this method isCdValue for every input given by the client. Therefore the method parameter cdValue changes for every input.

If it cannot be static then I would like to know how I can access this method. Please note I am primarily interested in learning about static of non-static method call. If it is a non-static call in a enum then how can we call this non static method. I am not trying to resolve the issue of how to get about checking the cdValue exists or not. It is just an example.

Answer 1

does the method isCdValue has to be static.

Yes, the method isCdValue has to be static here. An enum is a special kind of class. An enum constant defines an instance of the enum type. An enum type has no instances other than those defined by its enum constants. Hence new can not be used to instantiate an enum.

An enum type has no instances other than those defined by its enum constants. It is a compile-time error to attempt to explicitly instantiate an enum type (§15.9.1).

Refer this