code.java

public class CLASS {
  protected Father bar;
  public Father bar()
    {
      return this.bar;
    }
}
public class Father {
  ...
}

public class Son
  extends Father
{
...
}

public class GrandSon1
  extends Son
{
...
}

public class GrandSon2
  extends Son
{
...
}

public class Code {
  public main{
    Father A = foo.bar();
    GrandSon1 B = (GrandSon1)A;
  }
}
//This give me the error:
//"Cannot cast B to A because B type is GrandSon2."