How do I check a string is empty or null using if statement in Java?

Question

I need to get the enum itself first by using RegoDocumentType.getByValue(createOrderRequest.getIdDocument().getIdType())

Then check for null value, if it is not null, it will return the enum value. Else, it will return the createOrderRequest.getIdDocument().getIdType() as default.

So how do I refactor the code to only use one if statement to cater for both NRIC/11B and FIN smag value to rego value using RegoDocumentType enum?

Here's my enum:

public enum RegoDocumentType {
    
    NRIC_11B("NRIC/11B", IdentityType.NRIC.toValue()),
    FIN("Employment Pass", IdentityType.EM_PASS.toValue()),
    ;
    private static final Map<String, RegoDocumentType> BY_SMAG_VALUE = new HashMap<>();
    static {
        for (RegoDocumentType identityType : values()) {
            BY_SMAG_VALUE.put(identityType.getSmagValue().toLowerCase(), identityType);
        }
    }
    private final String smagValue;
    private final String regoValue;
    RegoDocumentType(String smagValue, String regoValue) {
        this.smagValue = smagValue;
        this.regoValue = regoValue;
    }
    public String getSmagValue() {
        return smagValue;
    }
    public String getRegoValue() {
        return regoValue;
    }
    public static RegoDocumentType getBySmagValue(String smagValue)
    { return BY_SMAG_VALUE.get(smagValue.toLowerCase()); }
}

Answer 1

    String something = "";
    if(something == null || something.isEmpty()) {
        // return A
    } else {
        // return B
    }

or

    String something = "";
    return something == null || something.isEmpty() ? [value A] : [value B];

Answer 2

createOrderRequest.getIdDocument().getIdType() seems to be a String in you case. You cannot return a string from getBySmagValue . Consider returning null or throwing an exception instead:

public static RegoDocumentType getBySmagValue(String smagValue) { 
    if (smagValue == null) reutrn null;
    return BY_SMAG_VALUE.get(smagValue.toLowerCase()); 
}

or

public static RegoDocumentType getBySmagValue(String smagValue) { 
    if (smagValue == null) throw new IllegalStateException();
    return BY_SMAG_VALUE.get(smagValue.toLowerCase()); 
}