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Thang Pham
Thang Pham

Reputation: 38705

Java enum and if statement, is there a better way to do this?

I have an java Enum class, and at runtime I will read in a value from command line, and I want to correspond this value to a value in my Enum class. Shipper is my Enum Class. Is there a better way do this this, instead of if and else if below? This look ugly. 

private List<Shipper> shipperName = new ArrayList<Shipper>();
...
public void init(String s){ 
    if(s.equals("a")){
        shipperName.add(Shipper.A);
    }else if(s.equals("b")){
        shipperName.add(Shipper.B);
    }else if(s.equals("c")){
        shipperName.add(Shipper.C);
    }else if(s.equals("d")){
        shipperName.add(Shipper.D);
    }else if(s.equals("e")){
        shipperName.add(Shipper.E);
    }else{
        System.out.println("Error");
    }
}

Here is my Shipper.class

public enum Shipper
{
    A("a"),
    B("b"),
    C("c"),
    D("e"),
    F("f")
;

    private String directoryName;

    private Shipper(String directoryName)
    {
         this.directoryName = directoryName;
    }

    public String getDirectoryName()
    {
         return directoryName;
    }
}

Upvotes: 5

Views: 32782

Answers (3)

planetjones
planetjones

Reputation: 12633

Yes add the string into the enum's constructor (specify a constructor in the enum which takes a String) and create the enums with a text value of a, b , c. Etc. Then implement a static factory method on the enum which takes a string and returns the enum instance. I call this method textValueOf. The existing valueOf method in enum cannot be used for this. Something like this:

public enum EnumWithValueOf {

    VALUE_1("A"), VALUE_2("B"), VALUE_3("C");

    private  String textValue;

    EnumWithValueOf(String textValue) {
        this.textValue = textValue;
    }

    public static EnumWithValueOf textValueOf(String textValue){

        for(EnumWithValueOf value : values()) {
            if(value.textValue.equals(textValue)) {
                return value;
            }
        }

        throw new IllegalArgumentException("No EnumWithValueOf
                            for value: " + textValue);  
    }   
}

This is case insensitive and the text value can be different to the enum name - perfect if your database codes are esoteric or non descriptive, but you want better names in the Java code. Client code then do:

EnumWithValueOf enumRepresentation = EnumWithValueOf.textValueOf("a");

Upvotes: 6

Darkzaelus
Darkzaelus

Reputation: 2085

You can get an Enum from the valueOf() method:

public void init(String s) {
    try {
        Shipper shipper = Shipper.valueOf(s.toUpperCase());

        shipperName.add(shipper);
    } catch(IllegalArgumentException e) {
        e.printStackTrace();
    }
}

EDIT:

If it is not just a simple a -> A case, then it might be an idea to create a HashMap with key=>value pairs:

private HashMap<String, Shipper> map;

public void init(String s) {
    if(map == null) {
        map = new HashMap<String, Shipper>();
        map.put("a", Shipper.A);
        ... //b => B code etc
    }

    if(map.containsKey(s)) {
        shipperName.add(map.get(s));
    } else {
        System.out.println("Error");
    }
}

I hope this helps!

Upvotes: 3

JustinKSU
JustinKSU

Reputation: 4989

shipperName.add(Shipper.valueOf(s.toUpperCase()));

If the name doesn't always match the enumeration you can do something like this

public static Shipper getShipper(String directoryName) {
    for(Shipper shipper : Shipper.values()) {
        if(shipper.getDirectoryName().equals(directoryName)) {
            return shipper;
        }
    }
    return null; //Or thrown exception
}

Upvotes: 6

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