Why does "final" on a POJO throw compile error on a "new" with inline setters?

Why can I not write an "inline" object creator on a final class?

Here is the (non final) version of the class.

public class ValidationResult {

    private boolean isValid;

    private int statusCode;

    private String statusMessage;

    public boolean isValid() {
        return isValid;
    }

    public void setValid(boolean valid) {
        isValid = valid;
    }

    public int getStatusCode() {
        return statusCode;
    }

    public void setStatusCode(int statusCode) {
        this.statusCode = statusCode;
    }

    public String getStatusMessage() {
        return statusMessage;
    }

    public void setStatusMessage(String statusMessage) {
        this.statusMessage = statusMessage;
    }
}

Here is the new with inline setters.

                ValidationResult vr = new ValidationResult() {{
                    setStatusCode(55555);
                    setValid(false);
                    setStatusMessage("This snipplet is working");
                }};

I make the simple POJO class "final"

public final class ValidationResult {

    private boolean isValid;

    private int statusCode;

    private String statusMessage;

    public boolean isValid() {
        return isValid;
    }

    public void setValid(boolean valid) {
        isValid = valid;
    }

    public int getStatusCode() {
        return statusCode;
    }

    public void setStatusCode(int statusCode) {
        this.statusCode = statusCode;
    }

    public String getStatusMessage() {
        return statusMessage;
    }

    public void setStatusMessage(String statusMessage) {
        this.statusMessage = statusMessage;
    }
}

And with the same new-inline

                ValidationResult vr = new ValidationResult() {{
                    setStatusCode(55555);
                    setValid(false);
                    setStatusMessage("Huh??");
                }};

I get a

> Error:(23, 41) java: cannot inherit from final
> com.me.myproject.domain.ValidationResult

"cannot inherit" ?

Huh??

When you use double braces initialization, behind the scene you're making an anonymous inner class that extends ValidationResult class.

In Java, you're not allowed to extend classes with final keyword, hence the compilation error you're seeing.

Also, keep in mind the following drawbacks when using double braces initialization:

> - Obscure, not widely known way to do the initialization
> - It creates an extra class every time we use it
> - Doesn’t support the use of the “diamond operator” – a feature introduced in Java 7
> - Doesn't work if the class we are trying to extend is marked final
> - Holds a hidden reference to the enclosing instance, which may cause memory leaks