使用泛型结合两种方法

Question

I have two different boolean variables that are set very similarly and I want to create a generic method that can handle two different class objects as the argument.

Note: Area and HuntingField are two entities I've created using ebean.

Currently this is what I do in order to set the two booleans:

boolean isNewArea = (Area.find.where().eq("id", area.id)
            .findRowCount() == 1) ? false : true;
    if (isNewArea) {
        area.save();
    }

    boolean isNewHuntingField = (HuntingField.find.where()
            .eq("id", hf.id).findRowCount() == 1) ? false : true;
    if (isNewHuntingField) {
        hf.save();

These are the two different find methods defined in the corresponding classes:

public static Finder<String, HuntingField>  find    = new Finder<String, HuntingField>(
        String.class, HuntingField.class);
public static HuntingField find(String searchString) {

    return find.where().eq("id", searchString).findUnique();
}

and this:

public static Finder<String, Area>  find    = new Finder<String, Area>(
        String.class, Area.class);
public static Area find(String searchString) {

    return find.where().eq("id", searchString).findUnique();
}

Now I want to create a method that takes either a HuntingField type object or an Area type object as a parameter and uses the corresponding find method on that object and returns a boolean value:

public static <T> boolean alreadyExist(Class<T> obj){
    boolean isNewArea = (obj.find.where().eq("id", obj.id)
    .findRowCount() == 1) ? false : true;

But eclipse is telling me that find and id cannot be resolved or is not a field.

What am I doing wrong?

Answer 1

java.lang.Class doesn't have a field called id. See the javadoc here

Answer 2

You are mistaking the class for the finder.

public static <T> boolean alreadyExist(Finder<String, T> obj){
    boolean isNew = (obj.find.where().eq("id", obj.id)
    .findRowCount() == 1) ? false : true;

boolean huntingFieldExists = alreadyExist(new Finder<String, HuntingField>());
boolean areaExists = alreadyExist(new Finder<String, Area>());