I've got a class that implements Iterator with a ResultSet as a data member. Essentially the class looks like this:
public class A implements Iterator{
private ResultSet entities;
...
public Object next(){
entities.next();
return new Entity(entities.getString...etc....)
}
public boolean hasNext(){
//what to do?
}
...
}
How can I check if the ResultSet has another row so I can create a valid hasNext method since ResultSet has no hasNext defined itself? I was thinking doing SELECT COUNT(*) FROM...
query to get the count and managing that number to see if there's another row but I'd like to avoid this.
You can get out of this pickle by performing a look-ahead in the hasNext()
and remembering that you did a lookup to prevent consuming too many records, something like:
public class A implements Iterator{
private ResultSet entities;
private boolean didNext = false;
private boolean hasNext = false;
...
public Object next(){
if (!didNext) {
entities.next();
}
didNext = false;
return new Entity(entities.getString...etc....)
}
public boolean hasNext(){
if (!didNext) {
hasNext = entities.next();
didNext = true;
}
return hasNext;
}
...
}