Question

i have written the following method

@SuppressWarnings("unchecked")
protected <E extends Enum<E>> void populateComboWithEnumValues(Combo combo, E enumData, String defaultSelectionValue) {

    // populate commbo
    for (Enum<E> enumVal: enumData.getClass().getEnumConstants()) {  
        combo.add(enumVal.toString());
    }  

    // select default selection
    for (Enum<E> enumVal: enumData.getClass().getEnumConstants()) {  
        if(enumVal.toString().equals(defaultSelectionValue)) {
            try {
                combo.select((Integer) enumVal.getClass().getMethod("getSelectionIndex").invoke(enumVal));
            } catch (IllegalArgumentException e) {
                LOGGER.debug("an IllegalArgumentException exception occured");
            } catch (SecurityException e) {
                LOGGER.debug("an SecurityException exception occured");
            } catch (IllegalAccessException e) {
                LOGGER.debug("an IllegalAccessException exception occured");
            } catch (InvocationTargetException e) {
                LOGGER.debug("an InvocationTargetException exception occured");
            } catch (NoSuchMethodException e) {
                LOGGER.debug("an NoSuchMethodException exception occured");
            }
        }
    } 

How can i pass different enum types to the second argument? I know i coulnd’t create an instance of an enum, but initialising an enum means i will be passing a single value not the entire initialised enum as follows … Other enums would also be passed to the same method for Combo specifics

public enum ServerEnvironmentName {

    /** 
     * The CFD environment name. 
     * Selection Index
     */
    CFD("CFD", 0),

    /** 
     * The PIT environment name. 
     * Selection Index
     */
    PIT("PIT", 1),

    /** 
     * The SIT environment name. 
     * Selection Index
     */
    SIT("SIT", 2),

    /** 
     * The DEV environment name. 
     * Selection Index
     */
    DEV("DEV", 3);

    /** The input string to identify the environment. */
    private String envURL;

    /** The index value for view selection.*/
    private int selectionIndex;

    /**
     * Enum constructor to initialise default values. 
     * 
     * @param selectionIndex index value for view selection
     * @param envURL input parameter for environment
     */
    ServerEnvironmentName(String envURL, int selectionIndex) {
        this.envURL = envURL;
        this.selectionIndex = selectionIndex;
    }

    /**
     * Getter for the envURL.
     * 
     * @return the environment string 
     */
    public String getEnvironmentUrl() {
        return envURL;
    }

    /**
     * This method returns the index of the enum value.
     * 
     * @return the selection index
     */
    public int getSelectionIndex() {
        return selectionIndex;
    }
}

Answer 1

You probably want to pass the class, and not an enum instance:

protected <E extends Enum<E>> void populateComboWithEnumValues(Combo combo, Class<E> enumClass, String defaultSelectionValue) {...}

Here you have an usage example:

public class EnumTest {

    protected static <E extends Enum<E>> void enumValues(Class<E> enumData) {
        for (Enum<E> enumVal: enumData.getEnumConstants()) {  
            System.out.println(enumVal.toString());
        }  
    }

    public static enum TestEnum {
        ONE, TWO, THREE;
    }

    public static void main(String param [] ) {
        EnumTest.enumValues(EnumTest.TestEnum.class);
    }
}