Bug 155894

Description Wolfgang Knauf 2006-08-31 15:54:50 EDT

This sample comes from EJB3 programming where you can query for entity beans of a certain type this way:

javax.persistence.EntityManager entityManager = ...;
//Create a query ("select * from MyBean")
javax.persistence.Query query = entityManager.createQuery("from MyBean");
//"getResultList" returns a list with only items of "MyBean" !
java.util.List<MyBean> listMyBean = query.getResultList();

Compiler warning:
Severity and Description: "Type safety: The expression of type List needs unchecked conversion to conform to List<MyBean>"
Id = "1071"

The code above works fine, but I think the warning is correct. 

Quickinfo suggests "Extract to local variable" (see attached screenshot)

I created a small sample. 
"getArrayList()" is a method with a non-generic return value, same as "query.getResultList()". In "getArrayListGeneric()" I assign the return value of "getArrayList()" to a generic "ArrayList<Integer>". For this line the quickfix option is available.

  private ArrayList<Integer> getArrayListGeneric()
  {
    ArrayList<Integer> list = this.getArrayList();
    
    return list;
  }
  
  private ArrayList getArrayList()
  {
    return new ArrayList<Integer>();
  }

If I use "Extract to local variable" this comes out:
private ArrayList<Integer> getArrayListGeneric()
  {
    ArrayList arrayList = this.getArrayList();
    ArrayList<Integer> list = arrayList;
    
    return list;
  }

The newly inserted line contains the same warning ;-).
This can be repeated one more time with the some result
 private ArrayList<Integer> getArrayListGeneric()
  {
    ArrayList arrayList = this.getArrayList();
    ArrayList arrayList2 = arrayList;
    ArrayList<Integer> list = arrayList2;
    
    return list;
  }

and so on...