How to get enum values if enum class is parameter in method in Java?

Question

I have multiple enums. Here is one example:

   public enum Telomeres {

    TELOMERE_1("TTAGGG"), TELOMERE_2("TTCAAA");

    public String telomere;

    Telomeres(String telomere){
        this.telomere = telomere;
    }

    public String getSequence() {
        return telomere;
    }
}

I am trying to create method (with enum parameter) that loops all values of enum class and checks if String contains at least one of these values. Unfortunately I can't get enum values to check if string contains them. Here is the code, which illustrates problem.

public <T extends Enum<T>> boolean hasTranscriptionStopSite(Class<T> enumData, String chromatin) {

    for(T e: enumData.values()) { // I get error here
        if(chromatin.contains(e.getSequence())){ // Also I have problems here 
            hasTranscriptionStopSite = true;
            break;
        }            
    }
    return hasTranscriptionStopSite;                
}

I would be very grateful for any advise how to solve this problem or for correcting my point of view.

Answer 1

To get the enum values from a Class object, you can use Class.getEnumConstants() .

If you want access to the getSequence() function. You should use a interface:

public interface SequenceProvider {
    String getSequence();
}

public enum Telomeres implements SequenceProvider {
    /*
    ...
    */

    @Override
    public String getSequence() {
        return telomere;
    }
}

and change the signature of hasTranscriptionStopSite(Class, String) to guarantee, that T extends the interface:

public <T extends Enum<T> & SequenceProvider> boolean hasTranscriptionStopSite(Class<T> enumData, String chromatin)

Answer 2

Firstly, enumData.values() is syntax error.

public <T extends Enum<T>> boolean hasTranscriptionStopSite(Class<T> enumData, String chromatin);
                                                            ^^^

As you can see, enumData is declared as Class . the method values() does not exist within a Class even though it's a Class<? extends Enum<?>> Class<? extends Enum<?>> .

Solution:

• Enum<T> should have been used instead. or;
• In honor of reflection, keep Class<T> , but replace enumData.values() with enumData.getEnumConstants() .

Secondly, e.getSequence() is also syntax error.

for(T e: enumData.values())
    ^

As you can see here, T is a generic type which extends Enum<T> . You can either specify that T also extends Telomeres in the declaration of it, or cast instead:

if(e instanceof Telomeres)
   ((Telomeres) e).getSequence()

---

As a side note, from your code snippet it seems your function can be condensed within the if() block, and becomes:

for(T e : enumData.getEnumConstants()) {
    if(e instanceof Telomeres)
        if(chromatin.contains( ((Telomeres) e).getSequence()) ){
            return hasTranscriptionStopSite = true;

Answer 3

Solution using getEnumConstants. Following your example. First you are going to need an interface for the Enum if what you want is to pass different enums to the method hasTranscriptionStopSite:

public interface HasSequence {
    String getSequence();
}

The enum implements this interface:

public enum Telomeres implements HasSequence {

    TELOMERE_1("TTAGGG"), TELOMERE_2("TTCAAA");

    public String telomere;

    Telomeres(String telomere){
        this.telomere = telomere;
    }

    public String getSequence() {
        return telomere;
    }
}

Now you can both get the values from the enum and the sequence from each enum value:

public <T extends Enum<T> & HasSequence> boolean hasTranscriptionStopSite(Class<T> enumData, String chromatin) {

    for(T e: enumData.getEnumConstants()) { // THE ONLY CHANGE IS HERE
        if(chromatin.contains(e.getSequence())){ 
        hasTranscriptionStopSite = true;
            break;
        }            
    }
    return hasTranscriptionStopSite;                
}