Base Method Invocation on enum

Question

I'm learning about Java enums and I was wondering what is the best approach to check multiple enums for a matching value in order to call a specific method. I have defined two separate enums below that are used by getValue method's colName parameter to determine what method to execute. So the enum drives the method call. There has to be a more efficient way to do this than what I have below. Any suggestions?

I want to avoid having to do the below (pseudo code):

 if(colName.equalsIgnoreCase("ATTRIBUTEONE") || 
       colName.equalsIgnoreCase("ATTRIBUTETWO") || 
          colName.equalsIgnoreCase("ATTRIBUTETWO")){
             callAsStringMethod();
    } else if(colName.equalsIgnoreCase("ATTRIBUTEFOUR")){
         callAsIntegerMethod();
    }

My Attempt using enum:

 public class RowHelper implements IRowHelper
            public static enum StringAttributes {
                ATTRIBUTEONE,
                ATTRIBUTETWO,
                ATTRIBUTETHREE;
            }

            public static enum IntegerAttributes {
                ATTRIBUTEFOUR,
                ATTRIBUTEFIVE,
                ATTRIBUTESIX,
                ATTRIBUTESEVEN;
            }
            @Override
            public String getValue(String colName) throws Exception{    
                boolean colFound=false;
                Object retValue = null;
                for (EConstants.StringAttributes attribute : EConstants.StringAttributes.values()) {
                    if(colName.toUpperCase().equals(attribute)){
                        retValue = callAsStringMethod();
                        colFound=true;
                    }
                }
                for (EConstants.IntegerAttributes attribute : EConstants.IntegerAttributes.values()) {
                    if(colName.toUpperCase().equals(attribute)){
                        retValue = callAsIntegerMethod();
                        colFound=true;
                    }
                }
                if(!colFound)
                           throw new Exception("column not found");

                if(retValue instanceof String )
                    return (String) retValue;
                else
                    return retValue.toString();
            }
        }

Answer 1

Try this:

public String getValue(String colName) throws Exception {

    final String name = colName != null ? colName.trim().toUpperCase() : "";

    try {
        EConstants.StringAttributes.valueOf(name);
        return callAsStringMethod().toString();
    } catch (Exception e1) {
        try {
            EConstants.IntegerAttributes.valueOf(name);
            return callAsIntegerMethod().toString();
        } catch (Exception e2) {
            throw new Exception("column not found");
        }
    }

}

The method's now returning the appropriate value, according to the latest edit of the question.

EDIT :

According to Kirk Woll and Louis Wasserman's benchmark, looping through values is significantly faster than doing a try/catch. So here's a simplified version of the original code, expect it to be a bit faster:

public String getValue(String colName) throws Exception {

    final String name = colName != null ? colName.trim().toUpperCase() : "";

    for (EConstants.StringAttributes attribute : EConstants.StringAttributes.values())
        if (name.equals(attribute))
            return callAsStringMethod().toString();

    for (EConstants.IntegerAttributes attribute : EConstants.IntegerAttributes.values())
        if (name.equals(attribute))
            return callAsIntegerMethod().toString();

    throw new Exception("column not found");

}

Answer 2

Well, this is a weird design ._. Anyway, you can use enum, but I would something like:

public interface RowAttribute {
    String getValue(IRowHelper rowHelper);
}

public class StringRowAttribute implements RowAttribute {
    @Override
    public String getValue(IRowHelper rowHelper) {
         return rowHelper.callAsStringMethod();
    }    
}

public class IntegerRowAttribute implements RowAttribute {
    @Override
    public String getValue(IRowHelper rowHelper) {
         return rowHelper.callAsIntegerMethod().toString();
    }    
}


public class RowHelper implements IRowHelper {
    private static final RowAttribute INTEGER_ATTRIBUTE = new IntegerRowAttribute();
    private static final RowAttribute STRING_ATTRIBUTE = new StringRowAttribute();

    private static enum Attribute {
            ATTRIBUTEONE(INTEGER_ATTRIBUTE),
            ATTRIBUTETWO(INTEGER_ATTRIBUTE),
            ATTRIBUTETHREE(INTEGER_ATTRIBUTE);
            ATTRIBUTEFOUR(STRING_ATTRIBUTE),
            ATTRIBUTEFIVE(STRING_ATTRIBUTE),
            ATTRIBUTESIX(STRING_ATTRIBUTE),
            ATTRIBUTESEVEN(STRING_ATTRIBUTE);

            private final RowAttribute attribute;

            private Attribute(RowAttribute attribute) {
                this.attribute = attribute;
            }

            public RowAttribute getAttributeResolver() {
                return this.attribute;
            }
    }
    @Override
    public String getValue(String colName) throws Exception {
        final String name = colName != null ? colName.trim() : "";
        for (Attribute attribute : Attribute.values()) {
            if (attribute.name().equalsIgnoreCase(name)) {
                return attribute.getAttributeResolver().getValue(this);
            }
        }
        throw new Exception(String.format("Attribute for column %s not found", colName));
    }
}

Then you don't need to create more than one enum and use its power to iterate through the possible values. You would only need to make the methods callAsStringMethod/callAsIntegerMethod public. Another way is to insert the implementations inside RowHelper. Something like this:

public class RowHelper implements IRowHelper {
    public interface RowAttribute {
        String getValue();
    }
    private static final RowAttribute INTEGER_ATTRIBUTE = new RowAttribute() {
        @Override
        public String getValue() {
            return callAsIntegerMethod().toString();
        }
    };
    private static final RowAttribute STRING_ATTRIBUTE = new RowAttribute() {
        @Override
        public String getValue() {
            return callAsStringMethod();
        }
    };
    ...
    @Override
    public String getValue(String colName) throws Exception {
        ...
        if (attribute.name().equalsIgnoreCase(name)) {
            return attribute.getAttributeResolver().getValue();
        }
        ...
    }

}

Anyway, I don't understand in your method how you get the attribute value really without passing as parameter the colName to it.